The amount of ridiculous cheesy combos that you can work on botlane with one of these 2 is ridiculous.
Senna has wayyyyyyyyy too many healing and survivability when she gets ahead (only one kill required, and she snowballs non-stop)
Aphelios is just a pre-rework katarina, where smashing buttons usually works just fine. He has wayyyyyyy too many things on his kit.
Senna needs a big base damage reduction on her early base damage, with a small heal buff early on. So that she becomes a safe laning phase pick but a mid-game utility powerhouse.
Aphelios needs to be "damage reworked". Make him good against tanks OR against squishies. Right now he is perfect for both.
Additionally, right now Master Yi, Tryndamere and Ekko are overpowered.
Imo I'm not a trynda player, but he has been weak for quite a while, I would keep him strong for some more time.
Master Yi needs to be "difficulty reworked", he needs some skill added to his kit. a mini rework. I always thought on making master yi a tank melter, but weak against squishies (basic attacks deal bonus damage based on the enemy BONUS health, instead of pure base true damage)
Ekko is too safe. Easily balanced: nerf ultimate cooldown. Double it for god sake.