I like tied up Whumpees as much as the next person but you know what I love?
Mental Restraints
Whumpee being forced to hold still while they are beaten to a pulp while their s/o is held at gunpoint. Locking their arms behind their back, digging their own nails into their skin as to not make a move.
Whumpee who cannot scream or make any other sound because rough punishment awaits if they do.
Whumpee who is guaranteed to come back after tasks obediently because Whumper has something or someone they want.
Whumpee who cannot hurt someone else because their morals hinder them. Leading them into an even worse situation.
Whumpee having to do anything Whumper asks of them because blackmail material exists and got into the wrong hands. Or even better, has been faked but is good enough to ruin Whumpees whole life if they don't play nice.
The helplessness of being aware that they are physically capable to end all of this in a bloody mess. But the price is too high.