http://arrow.wikia.com/wiki/Mirakuru
Pros: enhanced speed, strength, senses, reflexes at a slightly below Deathstroke level. 
Cons:heightened aggression and Schizophrenia. Basically, he'd have visual and auditory hallucinations, and rages so intense, he'd develop tremors in his hands and body, depending on intensity
Lovely, thoughts? Keep in mind I have this as part of my plan for Grant. In the reboot of this game, Grant doesn't have any powers.