Five years ago, I had a great job with a great company. I did well, got promoted and put on a flagship project. I was partnered up with a work colleague (different role to me) - who I found challenging as they didn't want to be on the project and was very resistant to change. The work colleague moaned and complained to higher management which led to my managers considering putting me on a performance plan. At the time work colleague realised the impacts of what he had done and told me he was sorry and felt bad as he didn't realise all his moaning could have potentially led to my dismissal. (Previous to this, I had been a top performer in the company and have always got on well with my work colleagues.) I ended up giving my notice shortly after and have gone on to much better things. I still keep in touch with my ex-work colleagues from that company and we have regular social meetups.
Last month the ex-work colleague was made redundant. He has had 18 months pay. He asked me for help getting a job, so I was happy to give general advice and recommend a few agencies and companies in our industry I knew who had vacancies. However, he has now asked me to contact the agents and the company I am currently working at and recommend him and put in a good word for him for doing the role that I currently do.
On one hand, I think it would be nice to help but he did a very different job to me and I don't know how transferable it would be to mine.
On the other hand, I cannot forget that his actions led to a very tough patch in my career. I would not have left otherwise. Although in hindsight, leaving turned out to be great careerwise for me.
AIBU - Yes - give him a recommendation regardless.
YANBU - No - you've done enough already.