It's just a matter of knowing the AI, I guess- I read the guide to the Perfect World Champion on this forum that abuses Bison's crusher method and I got the achievement on the same day I bought the game (along with other AI abuses I noticed along the way, which I then added to the thread in question). I'd rate it only slightly harder than Street Fighter 4's braindead AI abuse, because in both cases you only use one move but HF will require you to change up your movement a bit (compared to SF4 where you just stay up in their face all day and don't worry about reversals).
I'm sure Perfect World Champion is more than doable with all the characters if you put in enough time to find the abuses, but none are going to work as effectively as Bison in my opinion because his AI abuse basically revolves around one single move (I can imagine Dhalsim would require you to learn what particular pokes stuff each character's attacks clean, taking absolutely ages). Frankly, Hyper Fighting is nowhere near as competitive as Super Turbo is so I won't be playing it again after I get the online done, most of the character's ST combos don't appear to work in HF and it's lacking a bunch of special attacks. Glad I got it cheap, I'll be going back to HD Remix.