Undyne, The Undying

Double Strike, Haste, Vigilance, Hexproof
sacrifice Undyne, The Undying after 12 turns
{t} target creature can't block
when Undyne, The Undying becomes blocked,
it deals damage equal to the defending players
current life total to blocking creature
"You'll have to try a little harder than THAT."
-Undyne, The Undying