XCOM: Enemy Unknown

Though the achievement description suggests that you need to complete a "Very Hard" abduction mission, what is meant is "Very Difficult," just in case there is any confusion.

Abduction missions almost always involve 10 enemies (I've had only 8, but very rarely), usually in four groups (two groups of 3 and two groups of 2), so plan on armament appropriately. Also, since your concentration is quick offense, remove any of those pesky medkits from your packs -- you can always re-do the mission, after you've gotten the achievement, if you lost anyone that you'd rather not lose.

It's important to have a saved game before receiving an Abduction Mission warning, as you'll also want a favorable map to choose to try this achievement on -- therefore, if you get the warning for an Abduction Mission in Mission Control and you performed several actions between the warning and your last save, you may want to cancel out of the mission, re-load your last save, re-perform those actions, and save right before the Abduction Mission warning happens (it will happen again, right about the same time). This way, you can accept one of the missions, see the map, and if it's not to your liking, quit and try again. When choosing, keep in mind the primary qualification, that the mission be "Very Difficult."

Now, the map you're looking for is a relatively open map, with few/no buildings, just cover objects, so alien groups have no places to hide in multi-story buildings from your rocket attacks/snipers with squad sight. I find such maps much easier to navigate quickly for just such an operation.

For my group, I brought along 2 Heavies (2 rocket launchers were key in my mid-level group -- no colonels to double up rockets), 2 sprint-perked Support troops, one Assault troop perked to rapid fire at the end of his dash, and just one Sniper. Had my group been all colonel-level soldiers, I would more likely have brought 2 squad-sight-perked Snipers with the "In the Zone" perk and Archangel armor, and perhaps 2 sprint-perked Support soldiers with Ghost armor, so they might sight out alien groups without activating those groups -- if the aliens don't see the spotters, they don't bother going into hiding, making the "In the Zone" perk of the Snipers quite lethal -- (and, maybe one Heavy and one Assault to round out the 6).

With such an open setup, you might even finish the mission in 3 rounds, not 5. Good luck!

Additional notes: Keep in mind, that as you launch satellites over more countries, those countries will cease to have abduction raids launched against them, so if you reach full satellite coverage before getting this achievement, you may need to achieve this in an earlier save or a new game.

I got this naturally in Classic Ironman at the service station. The small service station with an attached building where you start at the pumps, not the truck yard. A group of mostly Squadies with no double tap sniper, so I think this will come naturally for most people in Classic. I moved a heavy into rocket range of the building in turn 1 and positioned the rest of my squad for crossfire. Blew the building open with a shredder (there was already a group or two of mutons/beserkers moving in), and had the entire map aggroed by turn 2 or 3. I think we were clear after 4. This was month 4 or so and the entire squad had plasma weaponry. I'm guessing mutons are your friend for this achievement since they like to make half moves and blood call when running away instead of full retreats or liftoffs. Scopes instead of defensive items should be a no brainer.