This spell thief champion will be so badass even Rubick would be jealous

But first these three themes MUST be true in order for the theme to work in League:

1. The Champion must be either from Zaun or Piltover. I prefer Piltover. He'd have a technomage theme similar to Viktor but only tangentially as his spells would be more utilitarian and basic like a shrapnel bomb as opposed to LAZER ARM OF DEATH.
2. The champion's main weapon should be knives/knife; it's concealed, dark, and iconic to psycho. The Champion copies his targets' ultimates by cutting out a piece of them and using the DNA to forge a mask (similar to looking at a friendly disguised Spy).
3. The guy is a psychopath. Not kinda, sorta crazy in the lovable way. No. The guy opens his closet and strokes his collection of the facsimiles of faces his machine has made. All of them. Individually. For an hour. He has a picture of Jinx on his dresser with love notes scrawled on the side, and when he comes home after a hard day of murderwork, he caresses the picture and kisses it, then licks it and swears he will capture that beautiful face of hers. That kind of insane.

Now, mechanically, he needs a versatile kit that has little synergy with itself i.e. by himself he poses little threat but with a team he can perform virtually any role with virtually any items. So:

1. passive needs to be something that does not interact well with QWE but is a good innate for an ultimate pair. Since he is obsessed with Jinx, I suggest something in the same vein as Let's Get Excited! but with a different niche (less or no snowball but still referencing the theme.)
2. QWE can't interact with each other well but when comboed with R, do amazingly well. One example would be to have Q be a linear passthrough skillshot that functions as waveclear while W would be a single target vulnerability spell and E would be some form of CC that is only beneficial when the champion is trying to disengage and not when trying to follow up.
3. His base stats would need to be crap since he could potentially use Malphite's ult one fight then use Ahri's ult the next fight because the circumstances dictate the champion should use a different ult. That kind of utility would mean that the champion, if they built carry or assassin, would have to be a late game champion.
4. He steals his allies' ults. Just for a short time. He steals the ult, ally cannot use their ult right now. He uses their ult, and their ult has a small (5-10 second) waiting period before they can use it. This prevents you from being able to chain the exact same ult too quickly. The champion can steal an ult that is on cooldown, but it freezes the cooldown for the duration of the wait time (5-10 sec).
5. He steals allies' ults only. This means the enemy doesn't have to worry about picking a champion whose ult would also screw over their own team.
6. The ult does not have to have a use in a 1v1 situation other than POTENTIALLY passive stats. He's not supposed to be able to duel; he has to screw over work together with his team

And one last thing: he needs an interaction where when he kills an enemy under certain conditions, they burst out into laughter while dying. and maybe draw a smiley face on the ground where they died.

Better yet: the death screen of the enemy has a giant smiley face on it until they respawn.