"He is discontented with himself."
Translation:Li estas malkontenta pri si.
Mem is not necessary in this sentence. I'm not sure how its use can be justified here. My sense is that it implies a context where he's saying "I'm not disappointed with X, but rather I'm disappointed with me."
Note: my original answer was downvoted, so I'm posting an expanded answer. Hopefully the person who downvoted it will explain the concern, or maybe I'll be able to answer the concern here.
I've asked some other trusted experts about this sentence and one responded that "mem" adds nothing. A few proposed a context similar to the one I posted above. I'm still gathering information on this, and I will be back to clarify when I have the more information, but the take-away at this point is that "Li estas malkontenta pri si" already means "he is discontented with himself".
Edit: I've been informed that this sentence has been removed from the course and that it's been replaced by one without mem. Without mem it means simply that he's discontented with himself. With mem it means that it himself, and really himself, and only himself that he's discontented with.
Context for the sentence with mem might be to clear up a misunderstanding or to specify ... it's not you... but...