we don't truly appreciate what we have until it's gone

— family members regret abandoning the mc's with their abusive neglectful mother and vile servants after they finally take custody of them.

— after fl a previous villainess undergoes a severe personality change those around her realize they may have misunderstood her, ml regrets his initial mistreatment and prejudice the more he gets to know fl.

— after a constant loop of repeatedly ending fl's life for the sake of revenge against her father, ml now in his current life learns to heal with fl and seeing her ptsd from his past killings fills him with guilt.

— ml will eventually regret any hurtful actions towards fl after a huge misunderstanding is resolved, he also comes to regret his mistreatment during their first introductions and start of their relationship as owner and pet.

— in the first few timeliness father neglects his daughter in favor of her dead mother causing the death of their entire family, in the new timeline he finally realizes and regrets his neglect when it's pointed out that his daughter had also lost her mother that day.