He is shown wielding a sword, therefore his name is his weapon.

Hint: Their name matches to their weapon.

Who is the "main character" out of all the Phighters?

Yea, the "ban" hammer doesnt ban people. (in roblox.)

He COULD be first aid, but his name is Medkit.

Cherry Blossom would be a good name too, but its Vine Staff.

In the trailer he is also referenced as the Crystal Criminal, therefore both answers are accepted but I'd prefer if you called him Coil.