Ultron got such a shit deal as a movie villain.

Him making jokes took away a lot of his menace. It might not be the most exotic, but I do believe he would have worked as a serious straight-laced psychopath who could maybe have some straightman interactions with the cast, like many comics of his.

Kinda like in the god-tier piece of media MGR;
Bladewolf boasts about his AI intellect for intimidation.
Raiden, sarcastically: "So why are we here? What's life's purpose"?
Bladewolf, very serious: "I'm here to kill you."