Depends on what criteria you look at. Splash is obviously useless.
Constrict only has power 10. There are a few others with that power but they hit multiple times.
The OHKO moves (Fissure, Sheer Cold etc) are pretty stupid because they rarely hit, and only when the opponent is lower level.
And of course, there's Struggle. You only use it when you've run out of all your good moves, so you're almost certain to faint soon.