I think if my main oc (you may have recognised him before) had a video game music theme, it would possibly be the universal collapse [Terraria calamity] or Infinite [Sonic Forces]
If bossfights had video game music; Stained, Brutal Calamity (Terraria Calamity); Find your flame (Sonic frontiers); Darth Revan's theme (Star wars The Old Republic); Undefeatable (Sonic frontiers); Soul of Cinder (Dark souls 3); Taurus demon (Dark souls); Empress of light (Terraria); Razormind (Payday 2)