Almost all the bosses either give you a weapon to use, can be cheesed with spear jumping, or using a speed boost jump.

Satyr: Gives you a sword. Attack once and if he doesn't jump back, back up to dodge his attack, then hit again and repeat. If he does jump backwards, push forwards to him and hit again, and repeat.

Cerberus: Currently trying double spear tactics for jumping on top of arch. Speed Boost jump works.

Centaur: Gives trident, just poke him a few times. Double spear tactics work by jumping on column, throwing to coin room floor, then going back and throwing spear into invisible wall facing coin room as a ramp, but this is slower than just killing him I think. Speed Boost jump is an option.

Manticore: Gives you bow and arrows. Just keep shooting and walking backwards.

Griffon: Gives you bow and arrows. Just keep shooting and walking backwards.

Medusa: You get a bow and arrows, same as Griffon and Manticore.

Hydra: Speed Boost jump. Have not tested spear jumping but looks like it would be easily done.

Minotaur 1: Just grab the coin, no fight.

Minotaur 2 (Final Boss): Just spear the wall and jump to the coin (aka spear jump).