Board Thread:Questions and Answers/@comment-30088034-20170219194117/@comment-24821641-20170220013953

Well, he has 9999 LV when his file replaces yours, but he's probably using the human souls to mess with that since Frisk/Chara's LV goes back to 1 every time you reset.

The bullets are strange - based on Sans not using his unavoidable attack until you spare him I would assume the patterns aren't literal and just depend on how alert you are, like a monster's defences, but Flowey uses his surrounding attack even if you dodged all his other ones.

Monsters are damaged by intent to hurt, so being soulless Flowey could probably kill most of them easily, but it's not clear how attacking magic affects human bodies/souls.

And the Omega Flowey battle doesn't help at all since he's using six human souls there, so... I don't think we can really know his strength.

He does say he's killed everyone, though, so he has killed Asgore, just hasn't ever got the human souls.

Chara depends entirely on their LV and whether they're fighting a human or a monster. They can't do anything to a human they're 7-12 LOVE doesn't help at all here. If it's a monster, I assume they'd do exactly as much damage as Frisk does at the same LV.