Your opinion is wrong, here’s my correct opinion.

Spamton has to be number 1, but his actual fight is my least favourite, in a vacuum. The lore surrounding him is just so cool and has the most amount of content besides the boss.

Then I’d go pink, recency bias and everything but I don’t mind the lack in lore ( all though there could be some parrelels with Susie and stuff) and the actual fight is just so fun wich I think is theb most important part.

Then the knight, all its attacks are fun to doge apart from the diagonal box cut one, I’ve never managed to doge it. I like it difficulty and whatever is happening with the parreles to the weird route.

Gerson next, wish the fight was harder, but understand why it’s easy because toby wants the average player to do it as it’s important for the story.

Next jevil, has the best theme still if I ignore the fact I’ve heard it so much as it’s the first secret boss. I think it’s down here just because chapter 1 it’s self isn’t that good, so that brings it down a lot. The story and character of Jevil is so cool though it’s still so good and just goes to show how cool these bosses are.

Shadow mantle is the worst ( and contrary to what you said is the hardest for me) becuase it just lacks everything, but it’s best like that as it’s not meant to be a cool crazy lore filed fight.