In a game, when you are feeling particulary aggressive and can get a good handle on your opponent, a dump tackle can be used.
This tackle is particularly taxing on the person you are tackling, as the end result is you slamming the person on the ground on their back. But, rugby is a brutal game, and really, if they wanted an easy sport they should have taken up tennis.
It can be considered to be dangerous play in a game of rugby, but referees can be forgiving and allow such moves. Dump tackles are also a notorious crowd pleaser.
"Be confident. Hit the ball carrier hard at the point of contact. Don't allow them to control the situation"