I'll use 252 HP/220 Def/36 Spd bold Zapdos with Leftovers
STONE EDGE - CASE1
CAP 6: 350 Atk (Adamant)
No field modifiers
46,35%-54,42%, very, VERY slight chance to 2HKO. Zapdos can outspeed and Roost off.
STONE EDGE - CASE 2
CAP 6: 350 Atk (Adamant)
Stealth Rock up
71,35%-79,42%, clean 2HKO, but, again, Zapdos can Roost.
STONE EDGE - CASE 3
CAP 6: 525 Atk (Adamant + Choice Band)
69,01%-80,98%, 2HKO. Probably this time Zapdos is slower, so, it won't be able to Roost off.
STONE EDGE - CASE 4
CAP6: 525 Atk (Adamant + Choice Band)
94,01%-105,98%, good chance to OHKO.