Baltizor, The Darkin Punisher

This is a champion model that I had in mind. I can't make any fancy splashart but I would like some feedback on the idea.

Baltizor The Darkin Punisher

Role: Marksman/Assassin

Passive (Cruelty): When Baltizor kills an enemy minion, he gains 5 attack damage for 3 seconds. When the Punisher kills an enemy champion, he gains 30 attack damage for 6 seconds.

Q (Whip): Costs 4% current health. Lash an enemy to deal 60/75/90/115/130 (+70% AD) and slow them for 30% for 1 second. (CD: 11/10/9/8/7 sec.)

W (Delayed Pain): Costs .3/.5/.7/1/1.2% current health per auto attack. Toggle: When active, your auto attacks only mark your target, dealing no initial damage. After a marked target has gone 3 seconds without taking damage, it will receive 105/115/120/130/140% of the damage that would have been dealt as physical damage.

E (Shadow Shift): Costs 7/6/5/4/3% current health. After channeling for .5, Baltizor moves through the shadows to the targeted position. (CD: 18/16/14/12/10)

R (Mass Execution): No Cost Mark all champions in a circle around you for 7/8/9 seconds. Any damage dealt deals no initial damage. The marks deal 125/140/165% of the damage that would have been dealt during the duration of Mass Execution to all marked champions once the duration is over.(CD: 120/100/80)

Appearance/Lore: Baltizor is another one of the last five Darkin. He uses methods of torture to punish corrupt generals and cowards on the battlefield. He resembles Aatrox's general body structure, however he is shorter, more slender, and one of his wings was destroyed in battle. He uses two fiery pistol to auto attack, quickly sending glowing balls of energy to his target.

Playstyle: In lane he would most likely be very passive, as his all in potential is very low. He would struggle against aggressive adc'ss or those who outrange him. However, his late game potential with Mass Execution is extraordinary. He could Shadow Shift into the middle of a fight, use Mass Execution, and lay some heavy damage before falling or killing everyone.

Final Thoughts: I don't think this champion is completed, but the basic idea is there. I was going for a fun, innovative adc that doesn't use mana. I'd like some feedback on the overall idea or if he would be too OP. If you need me to clear anything up that may not be properly explained, just ask.