Warwick?

Thats the most likely explanation. After all Warwicks voice over had hinted at a connection between him and Jinx for a long time, so it'd make sense that he is involved in this series too.

If we see JInx we most likely see Vi and/or Cait

If we see Warwick we most likely see singed and maybe Ekko

Neat

It is NOT warwick, unless they Ret-con his current lore. Maybe its a pre-cursor to the research that would make Warwick.

Warwick in his current lore never successfully transformed while "Free". He was tied to a operating table when he Died. And his transformation ocurred when his corpse was dumped in a garbage place, finally awakening once it was complete and it "Jump started" his heart again. Not to mention, none of the green chemicals, or the contraption Singed attached to his back are present. This guy is a kid. Singed is no where to be found nor did he seem to have Hentchmen. The kid isnt strapped with any of the contraptions and on top of that, it doesnt match the description of his transformation.

One more thing: Warwick gets transformed quite some time after Vi and Jinx get separated. Chronologically this story should take place while he was still a criminal, and not after he was trying to re-form himself.

Im getting Warwick vibes from the man with the giant hat in 1:26

I would be very surprised if it isn't Warwick. When you go to the Warwick League Wiki page, under Lore - Read More, you'll find that He, Caitlin,Vi (duh), and Jinx (duh) are all major characters in Arcane, so we know he'll be in it.