Finished read this recently, was a pretty cool ending although not too sure how I liked certain aspects of it, but I think writing an ending that makes all your readers happy will always be a tough one, as people like different endings separately to how they like different genres.
Overall the action was cool the the MC becoming OP was done in a believable manner, although the story soon reached a point where he was "already OP", but made him more OP just for fun. But it was still tolerable, things still seemed like a challenge for the MC and the story was gripping enough with other characters getting some good screen-time too.
In other places it has been mentioned quite clearly that "solo" levelling ultimately didn't happen too much, like "solo" implies being alone, and so that was the only part that felt strange, but overall it was just him doing the levelling, so in that sense the title wasn't wrong.
Ultimately I judge a manga on if I will read it again, and I definitely will, so this is going into my favourites for sure.
Probably an 8/10, not any higher because of the repetitive nature of the story and lack of variety in the plot, which seemed to loop in a shounen style with every increasing stakes which were ultimately easily beaten. Which isn't bad in itself, but limits the maximum rating I could give compared to a show that did all the above and more. The MC didn't seem to have much of a character growth except right at the beginning, and then stayed the same for the rest of the story.
Also from what I understand this was made by just one person? I've heard that several times mentioned, maybe it's true or not, but if it's true then that gives us artists hope that we can make something without needing tons of assistants and editors XD