Well, it was hard but J.Burgers carried.
Toriel 00:00
Papyrus 00:55
Muffet 01:59
Asgore 04:05
Undyne 06:29
Asriel 09:35
Gaster 15:27
Sans 24:37 (Launched just after walking on the pad but cinematic is playing so it's ok.)
UF Toriel 29:28
UF Papyrus 32:17
UF Undyne 37:58 (UF Muffet was supposed to be before but doesn't matter to be honest.)
UF Muffet 1:00:14 (I didn't respawn so I basically need to kill myself but UF Muffet died.)
UF Sans 1:26:22
UF Asgore 2:06:48 (J. Burgers are really op and useful here and same bug as UF Muffet but UF Asgore died too.)
Nightmare Sans 2:27:16 (Nightmare Sans have some lags but I don't have any idea why he didn't take damage sometimes.)