Samson is unlocked when the player defeats two floors in a row without taking any damage.
Samson starts with 3 Red Heart containers and Bloody Lust. Every time Samson is dealt damage, he receives a damage boost that resets when he goes down a floor.
Health regeneration items like Yum Heart, Pyromaniac, and Placenta allow health regeneration after taking damage, and thus allow for more damage, both stat-wise and health-wise.
Cancer and The Wafer minimize damage taken from Sacrifice Rooms and can be incredibly useful to build a lot of damage and pickups, especially in combination with an excess of hearts. The Wafer in particular is incredibly helpful in Chapter 4 and beyond, where all taken damage increases to one full heart per instance.
Dead Bird, Best Bud, Smart Fly, etc: All of these items will add to Samson's damage increase from getting hurt, although, unlike Bloody Lust, the bonus of these items only last for the duration of a room.
Fanny Pack's chance of dropping a heart upon hit can cancel out damage to Samson while also buffing him.
Dull Razor can safely provide Samson's damage boost without needing to take damage.
Gimpy increases benefits from taking damage and feasibly adds more survivability from random soul hearts and half-heart drops.
Blood Oath is extremely useful on Samson, as its damage up effect stacks with Bloody Lust, meaning you will start every floor with a significant amount of damage up.
Anything which lowers health such as Dead Cat can make purposeful self-damage less reliable as a damage booster. For this reason, taking items from the Devil Room or the Black Market, which cost health for every item thus taken, is not recommended for Samson.
Tears Down Pills are especially bad for Samson due to his low starting Tears stat.
In the Bible, Samson was a supernaturally strong warrior who derived his power from his Nazarite vow, entitling immense strength to Samson if he did not cut his hair.
Samson first appeared in the Binding of Isaac: Wrath of the Lamb expansion. That version had only 1 heart container and a soul heart for his starting health, and his Bloody Lust item acted like a weaker version of Afterbirth's Lusty Blood item.
Samson was originally unlocked by skipping two Treasure Room items and killing Mom in one run.