After Freya's triple buffed demise in 10-man (not on this page due to general numbnutting and update muppetry...) we took on Mimiron, inarguably the hardest keeper hard mode in all of Ulduar. After some running around like headless (and broiled) chickens, flapping arms and screaming something among the lines of "IT BURNS! WHY DOES IT HURT SO?!", V-07-TR-0N succumbed to our tenacious efforts to bring it down.
Granted, we had a few out-of-the-line gear upgrades by now, but stilll no walk in the park. Good job.
Now, AoT, meet Algalon, Raid Destroyer, Devourer of Tears, Ascender to the Heavens and Leaver After One Hour. Jolly good fun, that one.