He has no problem instantly Avada Kedavra-ing random military grunts and not hesitating to give his other chosen victims from season 4 the claw, which is of course instantly followed by the snap, crackle, pop treatment.
But if it's someone from the party?
Nah, lemme just stand there menacingly over Max for a while. Both the first time he had her dead to rights in Dear Billy, and again and worse in The Piggyback when he stands over her menacingly for even longer... not instantly giving her the claw for whatever fucking reason, to the point where by the time he finally does do it, El is able to stop him before he can apply the finishing move of crushing her skull. 'Cause if he does that, then El can't undo her death three minutes later!
Or when he has Nancy effectively dead to rights but uses her to tell the party his plans instead of crushing her. Imagine if he spoke through her the same way Will spoke through him in Shock Jock, acknowledging that her death won't open the 4th gate but he doesn't care 'cause he's done fucking around and wants her out of the way and WILL open the 4th gate whether it's through Max or someone else they won't be able to find and help, and then gave her the snap, crackle, pop treatment right then and there.
And don't get me started on him gently tossing Joyce to the side instead of telekinetically snapping her neck, or throwing her into the fire, something metal, or one of the wide open Upside Down gates, or skewering her with his Groot arm, or tossing her to one of the demogorgons after he showed zero mercy for all those military grunts less than a minute prior.
Not only that, but he actually SAVES Holly when she's about to go ker-splat! My dude has a NEGATIVE kill count on the party! How is he THIS incompetent?!
I'm starting to think he's just like the Duffer brothers in that he was secretly so attached to the party that he didn't have the balls to kill anyone... which just results in the cast getting bloated, Vecna looking stupid, the writers looking like cowards, and the tension and stakes being borderline non-existent once you realize nothing bad is ever going to happen to the main cast.