"The Peacekeeper makes every single gun at close range irrelevant. You will not beat it with any AR, Sniper, Smg, or Pistol in the game." - MagmaticWolf
Oh really?
Quick scope headshot from the Kraber. Sniper ✓
G7-Scout does over 50 damage on headshot even to purple helmet and has a rate of fire almost 5x higher. Sniper again ✓
R-99 has the 2nd highest non-headshot DPS in the game (minus mastiff). SMG ✓
Devotion has the highest headshot or bodyshot DPS in the game. LMG ✓ (assuming turbo charger)
R-301 has the 2nd hightest headshot DPS in the game (minus mastiff). AR ✓
Wingman has a higher fire rate and with skull piercing attachment does at least 84 damage on each headshot. Pistol ✓
Looks like you're wrong on all accounts.
Quick run down on TTK for each one of the above
assumptions made
purple helmet
full purple armor
full HP
100% accuracy / 100% of pellets hit
Peacekeeper assuming all pellets hit (headshot or not doesn't matter) = 1.03s
Kraber quickscope headshot = instant
G7-Scout all headshots = ~0.88s
G7-Scout all bodyshots = ~1.32s
R-99 all headshots = ~0.71s
R-99 all bodyshots = ~0.88s
Devotion all headshots = ~0.46s (assuming turbo charger)
Devotion all bodyshots = ~0.73s (assuming turbo charger)
R-301 all headshots = ~0.75s
R-301 all bodyshots = ~1.17s
Wingman all headshots = ~0.59s (assuming skull piercing)
Wingman all bodyshots = ~1.17s
BONUS peacekeeper can lose in TTK to the EVA-8 as well *
EVA-8 all headshots = ~0.94s
EVA-8 all bodyshots = ~1.41s
The only thing the peacekeeper needs done about it is have a slightly larger pellet spread so it isn't as good at range.