I want a novel that is completed and takes place in a mmo fantasy world where the mc is op. Give me some good recommendations.
Requiring them to be "complete" makes it difficult for me, though I do have at least one I can recommend...as most of the ones I can think of are ones which either aren't complete TL-wise, were dropped by the TL (Boundary Labyrinth and the Foreign Magician is a prime example of this, with the author done but the TL dropping it), or are still going on via the author themselves. Sadly the one I recommended is the one Zerak already mentioned. I will instead recommend some active TL ones that fit the criteria other than that, as it's the best I can do, heh: Different World Reincarnation as a Sage ~With my Gaming Knowledge, I’ll become the World’s Strongest~ - Same author as the Shikkaku Mon series. It's still fairly new, but the TL will catch up to the raws pretty fast at this point. This is a game world one. It's also an individual that is reincarnated multiple times in fairly quick succession early on, heh. Hone to Issho no Isekai Seikatsu - TL releases 2 chapters a week, though I dunno how many chapters the author has done I think that this is a game world one. I Became the Demon Lord and my Territory is an Uninhabited Island - The MC becomes OP very quick, becomes an adult very quick as well, etc. The TL is fairly sporadic (though still active)...and the story is fairly slow-paced overall from what I could tell. Might be up your alley, though...dunno. I Never Run Out of Mana - Title's self-explanatory, heh. Isekai ni Kita Boku wa Kiyoubinbode Subaya-sa Tayorina Tabi o Suru - MC doesn't start out OP, but becomes pretty OP pretty quick. Only in his own way, though...he's not undefeatable that I can tell. TL is still ongoing, but there's quite a few chapters done already. Think the author's still releasing as well. Isekai Tensei no Boukensha - TL finally started again, so I'd recommend setting this one aside until more chapters are done if you don't wanna check it out right now. Royal Roader on My Own - The TL is active and it's getting fairly close to completion now. The MC becomes "OP" through his game knowledge, though he's not undefeatable on his own. However, I still think you'll enjoy it if you want what's essentially wish fulfillment. ^^ This is a game world one. The Man Picked up by the Gods - See below, tbh. The Man Picked Up By the Gods (Reboot) - This is a reboot of the first version. The first version isn't bad, but it's missing a lot of things that could've made it much better. The reboot seems to be taking care of most of these (thus far)...and...the MC is definitely OP as hell. It's prety slow-paced, though. Still on-going, and the TL is actively TLing it...tough I think he's getting close to being caught up to the author's released chapters. The New Gate - I believe there's only a few chapters left of this to be TL'd, though the TL's got not set schedule for releasing chapters. This is a game world one. The Old Man Who Got a Second Round in Another World - This is a fairly unique one because the guy gets his memories of his past life back when he's like...in his 30s or some shit already. Either way, it's not bad. It's also not complete, though...both TL-wise and author-wise. TL is going at a pretty decent clip recently, though. This is a game world one. The Spearmaster and the Black Cat - This fits your definitions perfectly, other than the "Complete" part. The TL is still very far from catching up to the author, and given his release schedule it'll never happen until the author finishes the series. The chapters are pretty long, though. ^^ Again, these aren't complete, but some are fairly close, while others have a regular and/or fairly frequent release schedule. That's the best I can do with meeting what you seek, though. There's only a couple here that are "into a game world" ones, though. Still, I hope it helps some, heh. ^^
Stop, Friendly Fire! The same author of Everyone Else is a Returnee. In general all of the author's works are good and finished, but this has the most game elements in it.
Arifureta Shokugyou de Sekai Saikyou (WN) already have Anime adaptation while the web novel already completed the main story, currently translation still wait for author to release new after story raw. ugh its kinda hard to recommend another completed novel since the other already recommend it so i'll simply give you link where the translation is either already catch up or only few chapter till catch up with raw. Death March kara Hajimaru Isekai Kyusoukyoku (WN) currently the translation already catch up with raw though the story is still incomplete it took considerable time to finish reading it, also there's already anime adaptation as well. Isekai wa Smartphone to Tomoni currently the translation already catch up with raw though the story is still incomplete it took considerable time to finish reading it, also there's already anime adaptation as well. Konjiki no Moji Tsukai (WN) the story is about OP MC that unintentionally get dragged into hero summoning, he's quite OP, also there's already Manga adaptation as well. Tsuki ga Michibiku Isekai Douchuu the story is about OP MC that fight against Bitch Goddess and Racist Hyuman in order to protect other not Beautiful Being, also there's already Manga adaptation as well. Kumo Desu ga, Nani ka? currently the translation already catch up with raw though the story is still incomplete it took considerable time to finish reading it, also there's already Manga adaptation as well. Since i already recommend some japanese novel might as well i recommend some CHinese one where the MC is OP though its not as OP as the japanese one since the enemy is quite tricky and make use of strategy in order to fight against MC OPness. The Experimental Log of the Crazy Lich the story is about OP MC that got transmigrated into the game world one except that there's no Player there making it a bit harder than it suppose to do for MC though in exchange the MC were gifted with Catalogue about the Main Event of the game itself which mean he kinda now what'll happen in the future. Virtual World: Peerless White Emperor the story is about OP MC which work as retired Underground organization while he play the virtual game in order to earn money for living, the comedy were pretty hilarious especially the first 500 chapters so on. The Legendary Mechanic the story is about a Chinese Pro gammer got return into the past as an NPC prior the start of Galaxy Game, although at first the story is all about weak to strong by the time of Chapter 700 the MC already become OP enough to the point there's only less than 30 people that could fight against him in the Universe, also the story is still on going. lastly the Korean Novel where the MC is OP which is The Legendary Moonlight Sculptor the MC is quite lucky and become OP after he gain a special class which require him to Sculpture thing and make use of it as weapon.