Also to desert bluegrass: The Canon MPE65mm is pretty much the standard for super macro lenses, but there are at least two strong competitors out there, and they cost considerably less. One reason being that they are fully manual lenses, so working at high mag will likely require supplemental lighting. But people make it work. They come in more than one camera mount. I only know that they come in the Canon EF mount, and that is why I have my eye on them.
1) The Venus/Laowa f/2.8 25mm. This goes from 2.5X - 5X. This is a small lens with a narrow front element, which is nice for bringing it close to the ground. If ever I get a super macro, this is the one I'd pick for that reason.
2) The Mitakon f/2.8 85mm. This goes from 1X-5X. Early reviews found a problem with its optics (and those reviews will still turn up in searches for reviews of the lens), but reportedly the problem has been fixed so that more recent reviews are quite positive. One feature of note is that it has a longer working distance, which makes lighting easier.
Even post-fix I don't think I've seen any very positive reviews of the Mitakon. Edit:never mind I did find one.
I did find two reviews post-fix after a quick look-around. This one: https://petapixel.com/2020/01/23/back-f ... edesigned/ being sufficiently detailed to clearly show that the lens is now very close to the mp-e65, but the old Canon lens is still very slightly better. So that decides it for me as well.