Yeah, I invested in every single thing that increases pistol & headshot damage, have a crit chance of 47, and crit damage % of ~140. The surpressor I use increases damage by 2.5x when I shoot someone in stealth mode. There's a small range where enemies would notice their buddy dying so to combat that I've got cool and a cybernetic implant to help me.
The "cool" attribute increases the time it takes for enemies to become alerted, and I've got around 10 or so. So that's like an extra half second until one guy notices his buddy's missing a head. Next the cybernetic implant I have (don't remember name) slows down time by like 80% whenever I get detected (red eye icon starts to fill up, not actually alerted) which gives me roughly 3 - 4 seconds for me to do something in slow-motion. But despite the world being in slow-motion you don't actually move that much slower.
The end result is inst-killa things while hitting for 15K dmg at level 29. Heck, even my normal crits without being in stealth mode hit for 6k and that lowers enemies to 99.9% hp.