If you look around the net, there's a number of threads, articles and pieces of commentary that talk about this.
There are few yeasts that will naturally exceed the 20% mark (give or take 1 or 2 %).
Those often have compromises attached, like the resulting taste of the ferment, etc (I don't favour EC-1118, it's good for what it was developed for i.e. champagne, but seems to leave quite a bland taste when used for fermenting other musts). Yes, there are a couple of "turbo's" that claim like 23% ABV, but again, the compromise is often difficult to manage fermentation.
If you really want something strong, then just get some everclear and stir in some very strong flavoured honey. It will reduce the %ABV, but you'd probably still get something in excess of 80%
There's also some research that's been done into the highest level that produces the best tastes/flavours - I seem to recall that it was done with whiskey (Scottish ones), and the best flavours, aroma etc were released when it was watered down to about 20%
Also, if you're thinking specifically of meads, then don't forget, the higher the alcohol content, then invariably the longer it takes to age or the greater the amount of other additives that are needed to make it taste good......
S'up to you what it is that you actually want to achieve though, and just how much effort you're prepared to put into the ferment........
regards
fatbloke