SPOILERS
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He gets OP don't worry, it's a looong journey, but after a series of tribulations, he is the strongest hunter alive. Kim Giryeo is always saying that he is the greatest archmage and he is saying the truth, we get to see somo flashbacks of his alien life and he is basically a munchkin, he reaally is the soul most loved by mana.
You just have to be patient, but even before he is that strong, we get a lot of OP moments from him while still being an F-class: restraining a bunch of s-classes, killing s-classes (with a bit of help), and even in this arc gets two OP moments (SPOILER creepily killing the imoogi and it's owner)
And when he is finally SS-class, all the wait is payed. He gets so OP that he could move a whole ocean easily.
ALIEN FLASHBACKS?? LETS GOOOO I'm literally so curious what his culture and skills and life before he "reincarnated!" all we have is the brag that he's the most powerful and couldn't handle an eternity of nonstop office work lmao so curious how his species function as a society and also can I ask another spoiler
Does any sort of authorative aliens come looking for him? Cuz surely if he's that skilled someone will search for him and take him back by persuasion or by force no?
SPOILERS
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I don't want to spoil it too much bc all the revelations and twists are worth it (I really recommend reading the novel, the mtl it's not hard to read btw), but I'll say one thing that summarizes everything regarding your questions:
Don't trust Kim Giryeo's POV too much, more so about what he tells us in the first chapter. Sometimes he prefers to ignore the truth...

is the ml gonna be an OP charac or just a misunderstood charac?? answer plsss