Board Thread:General Discussion/@comment-36453001-20190724215038/@comment-39394247-20190725161747

Undyne the Undying has 99 ATK and [s]99[/s] 199 DEF (99 won't prevent a LV 17 Frisk from killing Undyne in fewer than 30 hits), and 1500 instead of 1095 HP.

Mettaton Neo has 30000 HP, 90 ATK, and 90 DEF. 30000 HP is enough that it takes more than 50 hits to kill Mettaton.

If you kill Undyne in a neutral run, Alphys tries to kill you in revenge, starting with Gaster Blasters outside the lab, and this goes like the fanmade Alphys Neo fight. Not hard at all compared with Undyne the Undying here.