Ekko is the best duelist in the game as well as a great teamfighter.

Note: I have not been stomped by an Ekko, ever. I'm simply noting some facts.

1. Ekko is the best duelist because his ult makes it so that if a fight lasts over 4 seconds (very common with duelist assassins, bruisers and melee carries like ) he can regain his HP and nuke you for 1.3 AP + 500 base. None of the duelists I wrote up there can handle a heal + that much damage; they can handle one or the other, but not both. He also has an execute better than Pantheon's crit because his execute starts at 30% HP and Pantheon's starts at 15%.

2. Ekko is also a great teamfighter because he can zone off an entire lane with a massive stun, zone off entrances to the lane with Q, and thus basically either deny a push or funnel the enemies into a single chokepoint. And if they don't respect his zoning? His team aces them just like if they got caught in 2 Amumu ults at once.

Ekko is the typical example of a champion that was designed with only laning phase 1v1 in mind, not realizing that his lack of reliability is irrelevant in a teamfight with their huge AOEs that allied stuns can set up. Ekko can be feeding 0-10 and still carry a teamfight with his utility/zoning, and building full tank, or he can deal massive damage while ahead. This is an example of a champ whose designer clearly did not think about how ridiculous his teamfighting would be and who forgot league is a 5v5 game, and 5v5s are not simply 5 sets of 1v1s.