Sadly no...vengeance wont activate off of defeated pets.
Badge Earned: Wing Clipper
A real showstopper!
Far too exploitable so I can't see it ever being possible to do this
Mind of Gaia lvl 50 Defiant's first Mind/Storm 'troller.
Deadly Doc 50 Dark/Dark Corr
and lots more on Pinnacle,Union and Defiant
Thought it would be too good to be true 
Life is one big practical joke that we as the human race have yet to see the punchline to. Once you work that out the rest is easy.
Aye, imagine a Necro/Traps with Vengence.
Detonator > Vengie > Extract Spirit > Resummon pet
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Aye, imagine a Necro/Traps with Vengence.
Detonator > Vengie > Extract Spirit > Resummon pet
[/ QUOTE ]Don't even need /traps, since you can target your henches after dismissing them (although you need very good timing).
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Aye, imagine a Necro/Traps with Vengence.
Detonator > Vengie > Extract Spirit > Resummon pet
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I'd swap the Vengie and Resummon pet; the dead minion hangs around for a fair while, and with the swap the resummoned one picks up the Veng buff too.
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Thought it would be too good to be true
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It would arguably make MoLRSF too easy as well if you could have regular vengeance off dead MM pets (because obviously for an MoLRSF attempt you can't get it off a dead player) - though I guess at least it would make MMs more wanted for the LRSF in general 
A simple (albeit possibly silly) question....
Can you activate vengance using a defeated Mastermind Pet as I am thinking of respecing and taking it.