Mobalytics - McGinnis by Seagull

We take Monster Rounds early game with Extra Regen to sustain through the early game
Prioritize walling off the enemy to get free last hits and push the enemy under tower so you can get some free denies and tower damage.

Split push once you get Intensifying Magazine as you'll start shredding towers and walkers (especially with monster rounds, which increases damage to structures)
Colossus is the key to this build: it massively increases your overall health pool and its 40% to all resists lets you out-heal almost anyone if you're in your heal radius!

Late into the game you'll likely need Lucky Shot and heal reduction of some kind (decay or toxic bullets)
Improved armors are also extremely useful
If you have the slot, Inhibitor is one of the strongest items in the game with this build.