Board Thread:Questions and Answers/@comment-27327020-20160404174206/@comment-26242189-20160806184513

Strongest in attack: Undyne The Undying at 12 ATK

Strongest in Defence: Asriel, Lemon Bread, and Reaper Bird, as well as one more that I don't remember, coming in at 9999.

Strongest in HP: Mettaton NEO, coming in at 30,000. That's 3 times more HP then Omega Flowey!

However, using data mining, there IS one person who surpases them all.

Gaster, coming in at 666666 HP, 66666 ATK, and 66666 DEF.