All Credits go to oG II GiiFT3D x from Trueachievements.com!This is at the beginning of the Catacombs.
You can get there after you have Beaten "The Worshiper" at the Graveyard.
You wanna keep on going till the second round room. There is a hole in the middle with wooden planks on top. Now Aggro the Big guy and let him walk across the wood, He will not fall down but bounce back up. at this moment keep you weapon 2handed and press
to Kick.
Just kick him down as shown in the video.
Good luck and have Fun.