I don't have high expectations for this one, especially with how overused this concept is in manga like this, especially in those following a longstrip format. Maybe I'll be wrong, but based on what I've seen from similar stories, it'll probably turn out as follows:
Protagonist gets betrayed and dies > Reincarnates into the body of a hospitalized young man > Turns out he was hospitalized due to bullying > He learns about his new body and what happened, temporarily not caring about the bullying while he 'figures things out' > Gets Harassed again by the bullies > Annihilates them > "Is that really ___" from every mob character > Gets noticed by a random girl > Gets sidetracked for twenty chapters without even mentioning the past or how he wants to get revenge (probably school activities/competitions/etc. where the protagonist absolutely NEEDS to show off how much cooler they are than the person that used to be in their body) > Eventually the MC gets noticed by someone with a connection to his past life (possibly the first and or second 'love interest') > Gets roped into some organization/family/whatever the fuck where he ends up working > Gets along with them > "Hey, these people thirty generations down the line are nothing like these people I hate, maybe I shouldn't get revenge on them" > Turns out the king is still alive or there's another otherworldly invasion and the Omega he killed before is back and stronger than before (maybe the king fused with one of those otherworlders to really make the enemy hate-able for the MC) > They fight > MC wins > MC spares him. For no good reason. Like you'll be sitting there staring at the screen going "wait, where's the revenge?" because the MC avoided it like the plague due to plot reasons (except for maybe one or two mob-level, comically evil villains that committed the sin of pursuing one of the MCs flock of women that is almost guaranteed), and then refused to take revenge on the subject of his hatred.
TL;DR: Revenge is probably bait, it'll just be a standard magic school harem where they justify the MC being a Gary Sue "badass" by having him be a crazy powerful sage with a past just dark enough to let the author be needlessly edgy and then do absolutely nothing with it.