build: underrail.info/build/?HgMFDQMMAwfCoMKgAAAAAMKgREcAAGJfAC5jADcARjYATisBOR1_NQJ-KkfCh0vChTNTwqXCtcKmw5fCncOcwp7DmW3ip74K4q-8BOKvvQHfvg
This build is a mega glass cannon designed to kill as many enemies with one shot each without giving them a chance to ever shoot back. It revolves around massive amounts of AP ( 50 base + 20 adrenaline + 20 PTC + 10 expert sprint + 20 blitz + at least 10 from rapid reloader = 130+ first turn) and reliable crits that will obliterate almost anything. In an ideal scenario assuming there are enough enemies to get the shooting spree procs you need(most fights wont, but if they don't you wont need that many shots) you can take 15 shots without the enemy being able to react: with max shooting spree spec and using a rapid spearhead you can take 9 shots the first turn, hit stasis and do six shots the second turn, which should clear just about anything. The build relies on Ambush to get reliable crits and max spec critical power to make sure everything is a one-shot. Ambush is suprisingly reliable when you can use premed+tk proxy as a reliable 0 ap silent light source. You can also lure enemies to better ambush spots (can make your own lit areas by pre-throwing flares) with flashbangs or just light them up with molotovs if you have to. Get Hoddurfurm ASAP as it provides a shadow around you to proc Ambush easier. The extremely high stealth and high perception makes it easy to set up from the perfect dark spot. For anyone you cant proc ambush on, that's what snipe, aimed shot, and chunky 12.7 shots are for.
If they survive that, the high agility and movement on this build makes it extremely easy to restealth and go again. On big maps you can literally just snipe a few, outrun them and restealth. You can also flash bang them or use vanishing grenades from Oculus if you want to make it even easier. Using flashbangs to split groups will make things easier as well.
Build choices rationale: 3 strength doesn't seem like enough to use sniper rifles, but I've found that adrenaline(+2 str) is so abundant with crafting its not a big deal, especially combined with the fact that you won't be using sniper rifles in the very early game. Also since you won't be getting hit, you can run with rathound regalia (+1 str) and rathound bbq(+1str) when you don't want to pop adrenaline. If you think it's too annoying you can drop some points from per. 5 dex for strafe because it makes popping in and out of cover with a spearhead so much easier. Premed and 55 PK for 0 ap tk proxy to proc ambush, and electrokinetic imprint is handy too. 13 agi for expert sprint. 70 TM for ptc and stasis. I think the rest is self-explanatory.
Equipment: 7.62 Smart rapid spearhead as your main weapon. 12.7 smart bipod harbinger to take shots with shooting spree when the AP cost doesnt matter(use it on the tough enemies). I used Regalia for most of the game but crafted an infused cave hopper leather armor for extra stealth and movement. It's nice to keep a Mini-Izu on the side to silently kill isolated enemies. Synesthetic Refocus is good to pick up for just a bit more accuracy and damage from the perception. Make sure you go protectorate for the gun oil.
Like most builds, the early game is rough and you'll mostly be using pistols and smgs so abuse stealth, throwing and traps as needed. The build really starts coming together once you have shooting spree at level 10. Cleared everything on dominating including the 4 squad training room in Heavy Duty(basically took out a few -> ran away -> restealth -> repeat).