Board Thread:Questions and Answers/@comment-27327020-20160404174206/@comment-27330113-20160806185756

. ..

Undying the Undying is 99 ATK and 99 DEF (Equal to LV 20 Chara)

Flowey is LV 9999 (Already explain why that makea him stronger than Chara)

Asriel is Infinite ATK and DEF

And the amalgamates can't be harmed due to their nature, just that (They even heal when receiving damage).