The next definition in rule 12 explains the sending off:
- Using excessive force is when a player exceeds the necessary use of force and endangers the safety of an opponent and must be sent off
Serious foul play is a sending off offence and it is described as:
SERIOUS FOUL PLAY
A tackle or challenge that endangers the safety of an opponent or uses excessive force or brutality must be sanctioned as serious foul play.
Intent doesn't come into it