Funny thing is that with Vader it’s not even in an indirect sense.

Mans absolutely could have canonically killed millions with his own two hands,

He got surrounded after crash landing on a dessert planet and the dude looks around and tells the commander calling for his surrender is “All I am surrounded by is fear, and dead men.”

IDK how they’d fare against each other in a fight, but Vader is definitely putting in the work to compete on Kharne the Betrayer’s million+ kill count, which we can only guess from that being how many people he’s killed that he was in control of himself enough to retrieve their skulls to offer to Khorne.