Ekko's Ultimate is awful to play against. [Not the damage, Im fine with that]
It not only gives massive mobility, but it heals massive amounts too. He can literally get bush baited into a 1v3, then just say NOPE and ult out. He can dive with ease due to his Q and W zoning incrediblly hard along with his E for gapclosing and his ult has a free escape. Its just so unfun to fight. A free frick up button.
And as Dominick Destine mentioned, he's entirely invulnerable during the activation.