Boss Guides#

Resident Evil 2’s boss fights take William Birkin’s G forms as their main spine, with Tyrant-class enemies alongside. This page collects each boss’s fight essentials and achievement conditions (sources: gamegene.cn, trueachievements.com); boss HP and damage numbers were never officially published and are not written here — before each fight, top up firepower per the ammo-reserve principle (see Item Collection).

Division of labor with other pages on this site: general mechanics like grab escapes, counter timing, and side weapons are in the Combat System; weapon locations and magazine sizes are in the Weapon Compendium; herb mixes and gunpowder crafting are in Item Collection. The story behind the boss fights (William Birkin and the G-virus) is in Story Analysis.

Boss Overview#

The stage divisions follow the main-story order: police station → parking garage / underground facility → sewers → NEST lab → escape. Leon and Claire each have a 1st Run (A scenario) and 2nd Run (B scenario) — four scenarios in total, and G1–G4 appear in both main runs. The B scenario’s puzzles and some mechanics differ from the A scenario (see Puzzle Guides), but the G-form fight nodes exist on both sides.

The same form plays very differently per protagonist: Leon’s high-power core is the Lightning Hawk magnum and W-870 shotgun; Claire relies on the SLS 60 revolver with upgradeable reinforced rounds and the GM 79 grenade launcher (locations in the Weapon Compendium). The tactics below are annotated against this difference.

G1: William Birkin’s First Form#

G1 is the player’s first G-form fight and hides the game’s most famous achievement condition:

• Achievement condition: while grabbed by G1, stab its giant eyeball with the Combat Knife.
• Fight essentials: G1’s giant eyeball is the mutation’s conspicuous weak point — keep distance and hit it with high-power weapons; don’t panic when grabbed — if you carry the Combat Knife you can counter-escape and hit the condition at the same time.
• Practical conclusion: confirm you carry the knife before fighting G1. Without it, being grabbed means eating damage and missing the condition.

The condition and the general counter are the same mechanic: the knife counter in the Combat System (stab the eye to escape a grab) is literally this achievement’s action — practice the counter and the condition comes free. Conversely, a nearly broken knife is about walking in unarmed: check knife durability before a boss room and swap for a fresh one at the item box if needed.

Background and firepower prep: G1’s body is William Birkin, who keeps mutating as the story advances — G1–G5 are stages of one mutation chain (story in Story Analysis, character relations in the Character Roster). For firepower, Leon should already hold the W-870 shotgun (Evidence Room weapon locker) by this stage, and Claire the GM 79 grenade launcher (same room) — both high-power options against the giant-eyeball weak point.

G2: Second Form#

• Achievement condition: drop it once using the crane.
• G2’s arena mechanic is the crane: lure G2 into the crane’s area of effect, and one activation completes the drop condition.
• Practical conclusion: this fight tests mechanic timing rather than firepower dumping; with low ammo the crane matters even more — one successful lure saves a lot of ammunition.

Firepower and arena details: the fight happens in the parking garage, where Claire can pick up the JMB Hp3 laser-sighted pistol from the police car trunk on-site — the condition tests mechanic timing, but this gun raises the margin for frontal suppression considerably; Leon’s line relies on the Lightning Hawk magnum obtained earlier (S.T.A.R.S. office armory — requires the S.T.A.R.S. badge that becomes the USB dongle when inspected; see Puzzle Guides).

The ammo ledger: the crane drop costs no ammunition, which doubles in value on Hardcore — Hardcore ammo is scarcer and pouches hold only 3 (Assisted/Standard: 6), so saving high-power rounds for G3 and G4 is this mechanic fight’s hidden payoff (Hardcore differences in Hardcore Difficulty).

G3: Third Form#

• Achievement condition: interrupt an object it throws.
• G3 throws objects at you; interrupting the throw as it winds up earns the condition.
• Practical conclusion: keep moving and watch the throw’s wind-up; fast-firing pistol/SMG-class weapons (Matilda, MQ 11, etc.) suit this condition.

Sewer-phase loadouts: each line picks up an “area weapon” here — Leon’s Chemical Flamethrower and Claire’s Spark Shot, both in the sewer storage room (location list in the Weapon Compendium). But neither is the first choice for this condition: interrupting throws is a contest of muzzle speed, and fast-firing, deep-reserve weapons like the Matilda (Leon’s starting pistol) and MQ 11 (Claire’s, from the S.T.A.R.S. office) are the right tools.

G4: Fourth Form#

• Achievement condition one: shoot it off the wall.
• Achievement condition two: defeat the G4 form with no less than 4 minutes remaining.
• The G4 fight carries a timer — a “timed + condition” double-pressure battle; item-box cleanup and ammo allocation must be finished beforehand.
• Practical conclusion: suppress the wall-crawl phase with firepower to shoot it down; to take both conditions in one run you must be fast and accurate at once.

Execution order: condition two’s timer counts down from the fight’s start, so preparation must be done before it — empty surplus items at the nearest item box, load high-power ammo, and put healing items in quick slots. On entry, suppress the wall-crawl phase and shoot it down (condition one), then pour the remaining firepower into beating the clock. The condition reads remaining time at the moment of the kill; positioning during the fight doesn’t affect it — what truly ruins the condition is a firepower gap, so stock enough high-power ammo for the whole fight.

Super Tyrant (Leon’s Endgame)#

• Achievement condition: defeat it with more than 5 minutes left before detonation.
• This is Leon’s timed endgame duel in the escape phase, where the endgame rocket launcher arrives to finish the job.
• Practical conclusion: the 5-minute condition means no stalling — plan your entry route and weapon-swap order in advance. Stacked with this fight’s timer, the S-rank evaluation makes Leon’s endgame the main pressure point for rank chasers (rank thresholds in Endgame Content).

Timer context and the S+ constraint: Leon’s S-rank thresholds are Standard A ≤3 hours 30 minutes and Hardcore A ≤2 hours 30 minutes (the B scenario has tighter ones — see Endgame Content), so the window left for this fight depends entirely on your overall pace. Hardcore S+ chasers should also note: S+ rules ban all infinite-ammo weapons and the infinite-durability knife, and saves are capped at 3 — this fight must be won with regular firepower; the infinite ATM-4 rocket launcher is the reward after qualifying.

G5 (Claire’s Endgame)#

G5 is William Birkin’s final form and Claire’s closing fight. The endgame Minigun (400 rounds) provides ample firepower budget, and the fight itself leans cinematic. After defeating G5, escort Sherry to complete the escape.

Contrast with Leon’s endgame: the Super Tyrant fight is a timed annihilation with a condition; G5 is a closing fight with a generous budget — ammo management is no longer the theme, and the focus shifts to evasion and output rhythm. The infinite Minigun unlocked by Hardcore S+ (Claire) is this weapon’s infinite-ammo version, and on replays this fight works as its firepower yardstick (unlock conditions in Endgame Content and Hidden Secrets).

Tyrant “Mr. X”: The Patrolling Stalker#

Mr. X is not a conventional boss-room duel but a stalker that freely patrols the station from mid-A-scenario onward:

1. Change routes when you hear footsteps: his patrol covers the main corridors; the expected value of a frontal encounter is always negative — a forced fight burns ammo and solves nothing.
2. Safe rooms are absolute blind spots: Mr. X never enters rooms holding typewriters and item boxes; when the chase gets hot, duck in and regroup.
3. Detour first: his existence is essentially a resource-management stress test — forcing choices between “the long way” and “pushing through the corridor,” which echoes the S rank’s “time only” design.
4. Side weapons only buy time: cornered with no retreat, grenades/flash grenades buy a few seconds to turn — the goal is disengagement, not damage; any thought of “dropping him” is burning ammo budget (side weapons in the Combat System).
5. Double the discipline on Hardcore: one hit means wounded, ammo is scarcer, and a single grab can end a run’s progress; on Hardcore, detouring isn’t a style preference but a survival requirement (mechanic differences in Hardcore Difficulty).

Other Tough Enemies at a Glance#

• G Adult: a sewer-phase tough enemy sharing the G line’s origin; encounter-fight in nature.
• Plant 43: a Claire-line NEST enemy tied to the herbicide puzzle; solving the puzzle comes before fighting.
• Ivy: a lab-area enemy; fire-based attacks have targeted effects (Leon’s Chemical Flamethrower rises in value here).

Unlike main-story bosses, these tough enemies carry no exclusive achievement conditions — fight when encountered, move on when done, pacing closer to beefed-up regular enemies. Plant 43’s entry point is the herbicide puzzle — grab the chemical and come back to deal with it, far cheaper than a frontal brawl (puzzle solutions in Puzzle Guides).

For a full bestiary of these enemies plus regular enemies (zombies, Lickers, zombie dogs, etc.), see the Enemy Compendium.

Universal Boss-Prep Checklist#

1. Ammo structure: keep a deep reserve for high-power weapons (Lightning Hawk / SLS 60 reinforced rounds) and enough pistol ammo as the floor.
2. Healing resources: at least one G+R+B mixed herb or First Aid Spray; on Hardcore one hit means wounded, so keep healing in quick-reach slots.
3. Combat Knife: the G1 condition and all-run counters depend on it; swap for a fresh one if durability is low.
4. Side weapons: grenades for escape windows, flash grenades for disengaging and regrouping.
5. Timed fights (G4 / Super Tyrant): walk the arena once to confirm mechanics and routes before starting — the achievement timers don’t allow learning the map mid-fight.
6. Gunpowder and crafting planning: Gunpowder, Large Gunpowder, and High-Grade Gunpowder (Yellow/White) are the base of ammo supply; finish your crafting plan before boss fights and convert high-grade gunpowder into your main weapons’ ammo types first — don’t improvise on the eve of a duel (the gunpowder system is in Item Collection).
7. Save discipline: Hardcore saves via typewriter ribbons with no autosave — manually saving before every boss room is an iron rule; lower difficulties have no such limit, but saving before a duel still saves an entire rerun.
8. Infinite-durability knife: destroying all 15 Mr. Raccoons unlocks the infinite-durability Combat Knife, zeroing out durability worries for the G1 condition and all-run counters (collection system in Collectibles).

How Difficulty Changes Boss Fights#

Of the three difficulties, Assisted auto-regenerates health and gives the most boss-fight margin; Standard is the baseline experience; Hardcore turns every boss fight into a resource reckoning — typewriter-ribbon saves, no autosave, one hit to wounded, only 3 pouches (Assisted/Standard: 6, each adding 2 slots), and scarcer ammo. On Hardcore the same run’s execution order almost needs a reshuffle: save first, prepare second, and every high-power shot on entry needs a defined target. The three difficulties’ full differences are in the Beginner’s Guide and Hardcore Difficulty.

No Boss Fights in Extra Modes#

Looking for “boss content within a mode”? The main story is the only place: in The 4th Survivor, HUNK fights from the sewers back to the station’s front door with no boss at all — all pressure comes from the zombie crowds and extremely scarce supplies; The Tofu Survivor shares the route and likewise has no boss. The four free “what-if” scenarios of The Ghost Survivors — No Time to Mourn, Runaway, Forgotten Soldier, No Way Out — draw pressure from enemy waves and exclusive zombie variants (poison-mist zombies, gas-canister zombies, lootable backpack zombies, and more), and No Way Out’s goal is holding the gas station against 100 zombies as Sheriff Cortini (70 in Training). The three modes in full are in Extra Modes and The Ghost Survivors.

Boss Fights in Ranks and Speedruns#

S rank reads clear time only: Standard A ≤3 hours 30 minutes and B ≤3 hours; Hardcore A ≤2 hours 30 minutes and B ≤2 hours — deaths, kills, and saves don’t affect the rank. Under this standard, G4’s 4-minute condition and the Super Tyrant’s 5-minute condition aren’t extra burdens but write “boss fights must be fast” into the rules — exceeding their timers won’t cost the S rank, but directly forfeits the matching achievement conditions. Speedrun magnitude reference: Guinness-certified 52 minutes 10 seconds for Leon A on Standard and 50 minutes 38 seconds for Claire A on Standard (2019–2020 figures; records kept falling afterward, cited not as current world records). The rank system and post-clear goals are in Endgame Content.

Achievement Conditions Quick Table#

The achievements matching these conditions and the full achievement/trophy system are in Achievements and Trophies; G5, G Adults, Plant 43, Ivys, and Mr. X have no matching conditions — handle them per each section above.