Assuming this is on master mode and I'm playing my primary class (melee):
King Slime: First boss, so expected, just walk away from him
Golem: Hilariously easy, especially since it's sandwiched in-between EoL and Duke Fishron.
EoW: Floating row of platforms invalidates it
Lunatic Cultist: Fragile and easily avoided
EoC: Easy until it's on the last few seconds but you'll probably kill it by this point
Queen Bee: Never does much damage, predictable attack pattern, quite fast near the end though
Skeletron: Lengthy fight, not difficult if you just circle around it though
BoC: Mobility helps here, otherwise Creepers can knock you into a stunlock, otherwise not too hard
Skeletron Prime: Circle around it, same deal as Skeletron, a stray bomb killed me once though
Destroyer: Laser spam, if I had less defense this would be tougher, mostly just lengthy fight
Plantera: Vertical arena helps with the spike balls, still a dangerous boss
Twins: Fast and relentless, though not as tanky as the other two mechs
EoL (night): Getting pattern down helps with this, as does the Rod of Discord, lengthy fight
Queen Slime: Projectile hell with crap flying everywhere, how is this pre-mech?
Duke Fishron: Could be lower, but the last phase is very risky
Moon Lord: Also a projectile hell and they're hard to see as well
Wall of Flesh: This is painful with melee, especially since I had no arena
EoL (day): Self-explanatory, you have to nohit it, I still manage it
Keep in mind I did EoL (both fights) pre-Golem so it was tankier than it would otherwise be. Wall of Flesh was probably the worst as far as my entertainment was concerned, Starfury is not a weapon I should have to be using for this fight and every time I attempted to build a hellbridge for it, I was swarmed by enemies so got frustrated and just tunneled through the Underworld Houses instead.