Though he has yet to appear in the MCU, Norman Osborn, aka Green Goblin, is the Joker to Spider-Man's Batman. Up until Venom came along, there was no question that the Osborns were Spidey's greatest enemy; since his return from the dead in the '90s Norman has become more of
a big-league player across all Marvel titles, so much so that he's essentially now the Lex Luthor of Marvel.
In the elseworlds story What If? Infinity- Dark Reign, Norman employs a team of supervillains to collect the Infinty Gems for him. He traps Spider-Man in a time loop that forces him to relive Gwen Stacy's death over and over and then uses the rest of the stones to take over the world.
Norman resurrects his abusive father to show him his accomplishments, but when his father remains unimpressed, he eradicates him from existence and accidentally erases himself from history in the process.