Bubbles to Dib

Depending on the story it's either Starfire, Jorgen Von Strangle, Heloise,Marceline or Twilight to Bender,

Hellboy, Blade and Silver to Protoman

Kain, Mike Corbey and Piccolo to The Shadow

Hades to Slade

Alternate Doofenschimtz and Darkwarrior Duck were this to Marceline's Dad. Now David Xanatos, Count Dooku and Jack Smith are this to Marceline's Dad

Black Star to Captain Knuckles

Dr.Doofenschimtz to Lucius Heinous VII

Galacta Knight and Tabuu to Dingo The Wolf

Scrouge to Eddy

Tarus Bulba to Uka Uka

Giovanni and Ozai to Malefor

Red Skull and Queen Chrystalis to Iron Queen

Black Doom,Zero Two,And Erazor Djinn To Malachite

The Hunstman, Sailor Galaxia and Polygon Man to Shinnok

Blackwood, Devimon and King Cold to Mungar

Nox Decious,Jim Moriarty,and T-1000 to Zeus

Terrance Lewis, Pitch Black, Hades (Kid Icarus) and Yakvone to Discord

Clu to Sigma

Lord of Darkness, Sebastian Shaw, Judge Claude Frollo and Gaston