Basically ALL his guns have something about them that is "broken".
The fact that his sniper rifle, gravity gun, and flame thrower all have global trigger range is stupid as hell.
The fact that Severum is a 550 range MELEE attack, the fact that it's ability prioritizes champions, the fact that he can move while using that ability
The fact that his sniper rifle ability has an invisible +100-235% AD ratio (since it gives him global vision and range for 4.5 second to land an auto attack... that can crit)
The fact that his flame thrower ability triggers a free auto attack against ALL targets hit, that doesn't use off hand ammo. So +100-235 AD ratio PER UNIT HIT, as well as the off hand weapons passive effect.
The fact that his kit auto levels, maxing all guns at level 9. Instead of skill points Aphelios gets bonus attack damage, attack speed, and armor pen. So he will ALWAYS have the most powerful versions of all of his abilities, while his opponents will have to pick one skill per level to get better at. Have fun between levels 3 and 13.
And let us not forget another HUGE PROBLEM. The fact that his Chakram refreshes his attack when he catches it. This passive feature means that he can pretty easily surpass max attack speed. Have fun getting attacked 3-4 times for each time you hit him.
I would also like to point out how the mini Chakrams refresh when they hit an enemy champion or epic monster. So if you are fighting a champion or epic objective, enjoy the free 30-363% bonus AD
Remembered hours later that his Turret has 550 range (same or greater then most ranged champions) and is untargetable / invulnerable until it activates. So if not triggered by minions, you HAVE to get hit to be able to hit this thing (even if you DO have more range then it)