The best map to do this in is Ilios in Greece. One of the points of capture is situated in a room in a building right next to the cliff of the map. Catching people just before they enter the side entrances, to the point, right at the start is a good way to get this done.
Another map in Ilios has the point surrounding a large well. Just as both teams meet at the point at the start, You can fire a concussive shot to land behind them and push them into the well.
Also a way to increase your chances of success is aim for characters that don't have any chance to recover, so for instance, don't expect tracer to die as she can rewind time, or another example is D.VA as she can just rocket boost back up onto the map.