Additionally, and probably most importantly, Luke actually isn't strong enough to defeat the emperor at the end. He losses. However, he wins over his father and that's what turns the tide.
Similarly, while Anikan has some mary sue moments, he has a far share of losses (chase for Padme's would be assassin, count doku fight, Obi-Wan fight, etc.)
I think the only time Rey "losses" a battle is in force awakens when she gets captured (but even after being captured she overpowers Ben almost immediately).