For those who wish to achieve this without cheating using dummy accounts and bots.
I randomly got this by camping in a corner with 3 sticky grenades on the wall, and when an enemy turned the corner, I exploded them, which sent him flying, and he somehow died from hitting the wall. I then tested this again at their spawn to see if it truly does work as a strategy, and I got it to work 2 more times out of maybe 4. The other 2, they were damaged so they died instead of being pushed fast and far.
Hope this helps :)