Aldo has taken on many types of fighters. Quite honestly, he's the guy I consider may be higher than Fedor on the P4P list.
Edgar and Mendes off a solid striking style to compliment a strong Wrestling pedigree, in fact Aldo has made a career off of wrestlers with mediocre striking, this is why Conor is such a good match up because he's more dangerous on the feet then anybody Aldo has faced.
To answer this question, People forget Mark Hominick, probably the best striker he has ever faced, and was one of the first to give Aldo some problems.