In standard English, we use the past perfect to discuss events which were completed before some other event. The past perfect is formed with the past tense form of "to have" (HAD) plus the past participle of the verb - on Sunday I had run ten kilometres before breakfast.
To express regrets about past events, we use the subject, followed by wish/wishes, followed by the past perfect (subject + had/hadn't + past participle). I wish I had worked harder at school, I wish I hadn't punched my manager, I wish I hadn't dropped out of college.
Using the conditional perfect 'would have/wouldn't have [done something]' instead of the past perfect is a mainly informal North American dialect variation, considered by many sources to be a mistake.
Regrets about the past
Mistake: I would have...