i did genicide run and didnt fight sans

[TheVinMan6]

after not fighting him I killed flowey but then sans called me and said to go to hell. i decided to do one last pasifist run and flowey was gone. did i mess something up because i cant get both pasifist ending without flowey like i did the first time. ( havent finished the secong pasifist run that im doing now)

[Danger Dwarf]

My guess is that mettaton neo said you were holding back in his fight. This means that you didn't kill everything at the core before his fight.
Step 1: Make sure you grind the area you are in until it says my name
Step 2: Save points should tell you how many monsters are left unless you are in the ruins
Step 3: The same goes for the core

[TheVinMan6]

also is there a way to change your true name?

[123lenah]

If you encountered Mettaton neo before killing all the enemies in the hotlands, then you will be forced back on the neutral path

The same rule goes for all boss fights

[(Edgy) Asriel Dreemurr]

Originally posted by VinMan6:

also is there a way to change your true name?

Only after a True Reset. (finish a Pacifist or Genocide Run)

[Brassqund]

Originally posted by VinMan6:

after not fighting him I killed flowey but then sans called me and said to go to hell. i decided to do one last pasifist run and flowey was gone. did i mess something up because i cant get both pasifist ending without flowey like i did the first time. ( havent finished the secong pasifist run that im doing now)

First, like say befoe,
you need to grind and kill every monsters until you get "but nobody came"...
and that before doing the boss of the area.

Second: don't mind if flowey is there or not.
That change NOTHING.
Also, after doing the pacifist ending, you need to
do the neutral boss again to re unlock pacifist.
Same after genocide...

[TheVinMan6]

but how do i know i killed every monster?

[(Edgy) Asriel Dreemurr]

Originally posted by VinMan6:

but how do i know i killed every monster?

Trust me. . . you'll know. Just keep killing, and don't fight Toriel until you kill EVERYTHING.

[Brassqund]

Originally posted by VinMan6:

but how do i know i killed every monster?

By reading my comment.

[Daku]

If your on the right track the music will be slowed down, save points will count remaining monsters, if 0 remain it will say "Determined". The BGM will change when encounters are depleted as well, otherwise the area's track will play in a slower speed.

If the BGM goes back to normal your back onto neutral route again.

And as noted above somewhere, do not whiff Mettaton NEO... if he dies telling you didn't put your whole heart into it reload the save.