Kinda surprised that there isn't a thread about this. I've started reading it on webtoons, which has a rather brief description:
"When you go from level 99 to level 1 and start all over again."
Also on some other sites, the description follows as:
"Those who clear quests, shall receive everything." An RPG adventure with HCLW and his allies, set in a lucid reality."
Which still isn't telling much. This is basically an isekai manhwa. If you are familiar with The Gamer, I'd say it's very loosely similar to that.
The story is about a cocky guy who is max level and basically the best in an MMO world which you can play during your sleep. One day, a strange entity with bugged powers comes, and kills HCLW, resetting him to Lvl 1 butt naked without any items. The story is about him finding allies (a big eater girl and a spoiled kid who is one of the successors of this game world) and using his game knowledge to rise again to the top.
If you like the isekai genre, I'd say this is definitely a must to read.
Check it out here:
https://www.webtoons.com/en/action/hardcore-leveling-warrior/list?title_no=1221&page=1