I Forget This Is Not Considered Common Knowledge - Tumblr Posts

This is a hill I'll die on: Vecna/One still has a massive exploitable soft spot for El.

Between:

The way he immediately swaps from pissy/killer mode to "augh...why are you crying..." when he spots El in 4.07

The way he seems completely incapable of getting around to physically harming her in any lasting way

The VR game Shadow Brenner telling Vecna that El's a weakness for him/She makes him emotional

The way he treats her in non-massacre NINA and TFS scenes

I feel like it's a pretty safe bet that deep down he's still very much attached to her.