If you have missed doing this in the campain fear not!
The quickest way to get this is via the "rumble in the jungle" map. Fight your way to the last map and kill all the goons there. Stay away from the batarangs for this phase of the fight. As soon as you have him alone, start planting explosive gel all over the place. As soon as he charges for you, he will step on the gel and will be stunned. Punch the hell out of him and the achievement is yours!
(video credit: WikiGameGuides )
Hope this helps you guys!
Any improvements? Please let me know in the comments below!