How can I roast my former narcissistic a-hole manager

Years ago, I worked with a narcissistic a-hole who had somehow weaseled his way to a cushy managerial position in tech. Extremely self-confident. Bully. Unqualified. Big talker. Nothing-doer. You get the idea.

He was my manager for just under 2 years and never promoted or advocated for me, but took credit for my work and ideas, which he presented to leadership as his. (Have insider confirmation on this from multiple people.)

Eventually (years later), he was fired. I had long since quit. Many people reached out to tell me when he got the boot because they all knew what I had to put up with back then. I then noticed that he updated his LinkedIn profile to list in detail all the programs and initiatives I worked on at that place, basically taking credit for my work. I'm not exaggerating.

I have obviously not been in touch with this person for many years and had no plans to ever speak to him again, until recently he reached out (I'm paraphrasing): "I've started a consulting gig and helping with XYZ but I haven't done that for a while. (XYZ literally listed on his resume as one of his accomplishments that were actually mine.) Do you have time to discuss?"

Of course, I know he is looking to get free know-how to then present to whoever made the mistake of employing him, but I play dumb: Heyyy, how have you been! I'm really busy, actually, and have no time for side projects. Best of luck!

A-hole has the audacity to write back and actually spell it out: "I really only want to get a quick download from you if you have 20-30 min."

The sad part is, he is so self-absorbed that I bet he doesn't even realize how obnoxious this is. I haven't responded. This group has come up with some fantastic advice in the past (I've been reading here for a while, using a throwaway for this though... idk why, fear of him seeing this? ugh).

So, yes, I know the mature thing is to not respond. But if I were to do it, what should I say to get back at him? Help me have fun with this!