i did a thread about this a year or so ago, chapters 3 and 4 dropped so heres the updated version
hardest to easiest
(link: https://tiermaker.com/create/deltarune-bosses-16930670 )
Explanations
S: Roaring Knight
shit is insane bro, you get hit thrice and it’s over for you, the shooting sword attacks are the worst. if a party member is down here, they’re dead for the rest of the fight unless you have a revive mint. (didn’t stop me from being its ass though)
S-: Snowgrave Spamton
fight isn’t too hard itself but you’re completely alone as kris and he deals a shit ton of damage, especially enraged
Jevil
I mean honestly you already know he’s difficult, it’s been 6 years there’s no need to explain
A+: Titan
The first time in deltarune history that a final boss is actually somewhat difficult, mainly because there’s a lot of random bullets on screen at a time and it’s difficult (or sometimes impossible) to dodge it all (SIGNIFICANTLY easier if you use the black shard though, would be 2 ranks lower in that case)
Spamton Neo (normal route)
FORMERLY the easiest secret boss, none of his attacks are very difficult except for the 3rd heart attack and the second phone attack.
Gerson
The new easiest secret boss, some attacks are difficult such as the blue shells, and I personally struggled a lot with the new diagonal green soul mode, but you can kind of just spam Susie’s heal and wait out the fight.
A: John Mantle
I have no idea why this guy fucked me up as much as he did, he’s really not THAT difficult, but it’s a very different style of gameplay than normal, takes time to learn
Jackenstein
Once again, different kind of boss than normal, kicked my ass mainly because i didn’t see the alternate exit on that one attack and kept getting ganked by the pumpkin.
A-: Tenna
Mostly minigame focused, its an onslaught that you’re basically guaranteed to come out of with very low hp, second hardest final boss in the game
Gerson’t
I didn’t do the secret boss on my first playthrough, so this was my first time doing green soul in a while (since undyne), took some getting used to but not that difficult (also you can cheese the fight by claiming you cant hear anything to susie, which will cause the white flashes to remain throughout the entire fight)
B, C and D:
everyone in these categories is easy and i’ve already talked about them in my last list except for 2
Rouxls 2: bisexual edition
would actually be difficult, except for the fact that you get a heal act if you’re low on hp, so it really isn’t
Weather guys, turns out they’re actually married and not siblings like we all thought! Whoops!:
somewhat difficult attacks, but too short of a fight to really matter
NOT RANKED: Mike
didn’t bother fighting him