Samson

Repentance 1.7.9 on PS5.

What you start with

The mechanics that actually govern this character.

3 red heart containers, tears -0.1, shot speed 1.31, range 5.0, speed 1.1. No damage multiplier.
Bloody Lust in Repentance gives flat, escalating damage: +0.5 on the first hit and +0.2 more on each hit after, reaching +1.5 on the sixth, for a maximum of +6.0. It resets on every new floor.
Child's Heart trinket (clear the Ultra Hard challenge) makes red hearts drop more often, which feeds the self-damage loop.
Bloody Lust carries over: any character who dies as Samson and revives as someone else inherits the item.

Bloody Lust resets on every new floor, so the six hits have to be re-earned each time. Take them early in a safe room, not during the boss fight where you need the damage already on.
Take the hits from sources that do not cost you deal chance: Blood Donation Machines, Devil Beggars, Sacrifice Rooms, IV Bag, Razor Blade, Sharp Plug and Blood Rights are all self-damage.
Health ups are damage ups for Samson, so Angel Rooms outrank Devil Rooms. Devil deals remove exactly the containers his damage engine consumes.
Stop at six hits. The bonus caps at +6.0 and every hit past the sixth is pure loss.
His 5.0 range is below Isaac's 6.5, so pick up a range item early or your shots die before reaching the target.
From Chapter 4 onward all damage is one full heart per instance, so build the rage in Chapters 1-3 where hits cost half hearts, and use a self-damage active from then on.

Strong on this character specifically, not just strong.

Dull Razor: it hurts him without removing health, so it fills Bloody Lust for free. Two-room charge, and it does not destroy the Perfection trinket.
Birthright: four extra Bloody Lust steps at the same +0.2 intervals, raising the cap from +6.0 to +14.0.
Blood Oath: the floor-start stab counts as one damage instance per half heart drained, so it fills Bloody Lust immediately and stacks its own exponential damage on top.
The Wafer and Cancer: they cap or halve damage per instance, which makes Sacrifice Room spikes and other self-damage cheap while still counting as hits.
Old Bandage, Yum Heart, Placenta and Fanny Pack: they refill the health he is spending, which is the limiting resource.
Cambion Conception plus Dull Razor: Dull Razor counts toward Cambion Conception's damage counter, so repeated use spawns permanent demonic familiars for free.
Gimpy: extra half hearts and soul hearts on hit, which directly subsidises the self-damage plan.

Picks that are neutral or good elsewhere and bad here.

Devil deals and Black Market items: every deal removes a container, and containers are the fuel Bloody Lust runs on.
Dead Cat: one container plus nine lives makes deliberate self-damage unreliable and removes the health pool entirely.
Abaddon: converts containers into black hearts, which he can still lose but cannot refill with Yum Heart or Placenta.
Saving Bloody Lust hits for the boss. They must be taken during the floor and are gone the moment you use the trapdoor.

Verified against 1.7.9 on console — anything patched, PC-only or Repentance+ only is called out rather than listed.

Dull Razor plus Car Battery triggers on-damage items twice per use, so Bloody Lust fills in three uses instead of six.
A Sacrifice Room is the cheapest rage farm: spikes count as self-damage so they neither reduce deal chance nor destroy Perfection, and the 3rd and 5th sacrifices each have a 67% chance of 'You feel blessed!' toward an Angel Room.
A Bone Heart does not break while it holds at least half a red heart, so it lets him feed Sacrifice Room spikes a half heart at a time indefinitely.
Blood Oath plus BFFS! adds two full hearts of bonus on top of whatever was drained, topping out at about +29.6 damage and +1.4 speed.

Boss Rush is one of his easiest marks: fill Bloody Lust in a Sacrifice Room immediately before entering, and 1.1 speed comfortably makes the 20-minute cut.
Bloody Lust resets on entering Corpse for Mother and on each Ascent floor for The Beast, so bring Dull Razor or Blood Oath rather than relying on taking floor damage there.
His Angel-leaning play naturally sets up the Mega Satan mark: refuse Devil deals, fight the angel statues, collect both Key Pieces.

Open the tracker for the ordered run queue, or how to unlock characters if this one is still locked.