Well, the stumbling block is that "you are a loser" is somewhat figurative in English. We use it to mean that person is generally useless and not worth our time. "Totus perdendum" is dog Latin. If that's the effect you want, then go for it! "Vinctus totalis" is something closer to "totally beaten (person)". Still, if that's what you want then use that. The best thing I can advise is to find a suitable English synonym for "loser" ("a failure"?), and see what translations seem best.