Cobra Commander vs. Serpentor
From G.I. Joe vol. 2 #25 during the Devil's Due run. The moment most Joe fans have been waiting for: Cobra Commander versus Serpentor. Winner gets rule over Cobra.
This was during Serpentor's big return arc #22-25 that the series was building up too. He had captured some Joes (biggest one amongst them being Snake-Eyes) and the Commander.
Of course the group escapes and once Cobra Commander alludes his newfound "allies" and all hell is breaking loose with Cobra and G.I. Joe vs the Coil (Serpentor's faction) on the former Cobra Island, the Commander decides it is time to leave when we get to this:
HA! God I loved that.
I know Zartan's kill was oh so more flashier, but come on those last lines the Commander said to Serpentor where just awesome.
For those wondering who the kids are, they're Serpentor clones, all various tries before the original. Cobra Commander ordered them killed, but Mindbender couldn't do it and in the first part to this arc was being father to them all. After the story they're all broken up and taken into foster care. One of them not included in this was aged and become's a US General during America's Elite. His name was General Rey and unlike the rest of his fellow clones wasn't too fond of the possiblity into turning into such a monster.