'Can't Touch This!' and 'Butcher of Blaviken' - I got both these at the same place. when you have finished the main quest in White Orchid you'll have to go back to the inn. Once inside the inn, you'll talk to someone, and then after the cut scene you'll be attacked by five guys, I mashed the X button and killed all five of them within a few seconds and got both achievements. I did have the most powerful sword you could get at that point, so I did one-shot them. I'm also playing on Death March, so on lower difficulties this should be even easier. Make a save before going into the inn.
I'm doing some testing on a few other achievements, so I'll let you know how I get on.
Considering you are probably still in White Orchid, I'll tell you where I few more achievements so you can test them.
'Fist of the South Star' - One of the first things you'll do in White Orchid is go to an inn and acquire some info, when you leave you'll be attacked by three guys. You can use Axii on one of them and the other 2 will attack you. Block the first guys attack, and them spam the Y button and you'll knock him out in 3-4 hits. keep your eye on the other guy, though, and make a save before leaving the inn just to be safe. I imagine there are quite a few places you could get this achievement, but this how I got it.
I'm sort of freaking out, since I'm sure I will get so incredibly frustrated doing that. This may seem like a dumb question, but is that whole process on the hardcore difficulty? (I know, I know… I just thought maybe the "hardcore" aspect came from restarting the whole game rather than the difficulty).
Thanks though. I'll keep that in mind when I start. At least I'll have 4 playthroughs to practice and I'll have the levels memorized by then.