Open idea for any interested author:
Most do-overs have a MC that either failed at life or died too young and wish for a second chance. How about a bored god/king/emporer (basically, someone who always had the power/influence to get whatever they want) who gets the opportunity to try a life of a "norm"?
ISTR that artie had a short one, where the sent-back dude went to save someone from injury/death, only to be killed by the vehicle that caused the prior accident. Not what you describe, but a definite reversal.
It might be difficult for the reader to sympathize with the one-time king, if he's now having to live an ordinary life, just like them and billions of others.
How to do that?
Or should the writer try to make him so hated that readers would continue reading, hoping something worse would happen to him?
What if say the king getting the do-over was cursed to live their life a second time as a commoner under a king similar to who he was before his curse?
The curse would include him reliving that life until a certain sequence of events occurred.
There are a few reverse isekai / light novels with this theme. MC is God-Emperor two lives in a row, hates the responsibility so his next incarnation is as a bottom level adventurer one step up from a peasant. Another trope is isekaied teens that complete the other-world quest, defeat the Big Bad and their consciousness is returned to their body at the moment they left it. Thus the normal SOL do-over issues of trying to reintegrate into a younger life after years of deprivation and slaughter. Trope inverted, the Big Bad is killed and isekais as a loser student in modern Japan.
Variations include the returned MC is able to recall magic items / powers from the other world, the modern Japan the MC returns to is now overrun by demons or zombies and time has passed there as well, or no zombies but time has passed and the MC has to reintegrate into society and explain away being missing for years while hiding the PTSD from years of fighting.
One of the thoughts I had after I posted this was about a slightly different scenario:
Top tier Master Rogue-style fighter in a medieval fantasy trope world (with or without dungeons/fantasy creatures) has developed extreme stealth, shadow-stalking, etc ... gets transported to a new world (medieval Japan) and uses his knowledge to start training a legion of shadow warriors thus introducing Ninjas to our historical timeline.