What is your hardest boss in Terraria?

[SimeaseKitten]

Obliviously Duke Fishron if you count the stats but WoF in one class playthrough and doing expert

 

[chapapote]

Duke Fishron, and I would vote for him even if Moon Lord was a possible choice.

 

[neoselket]

moon lord, but other than him, plantera in general, but wall of flesh in expert. i have never beaten him first try on expert mode.

 

[Darkstar01]

That depends, when do you fight the duke? If I get Cosmic Car Key, then he's not so bad, but without it, he definitely would be worst barring Moon Lord.

Expert Skeletron is Satan, but I'm not sure if he's actually worse than Duke Fishron or expert Plantera.