This is my first game I completed all achievements in, and I am horrible at fighting games so if I can do it, anyone can. For individual achievements, all of the guides on this site were very helpful, so I figured I'll write about them as a whole rather than be too specific. I'm also going to stay away from character recommendations as I firmly believe it's best to use whoever you know best (unless I'm asked, I won't mention it) and are the most comfortable with. Every character has their advantages, make the most of them.
All of the achievements basically fall into three categories: scenario campaign, arcade, and online. As most of them are in scenario campaign, it just requires time and patience. Once those are done, you're almost there.
I found the changing cameras the most frustrating, and key here is to not try to do anything fancy. Any move that takes time to execute will get interrupted. I got through it all mashing simple punch and kick moves. Hit RB as frequently as you can, as you will keep hitting the enemies long after they die for some reason, and many times your target will be the furthest enemy from you in which case you will hit nothing but air as a pile of enemies overwhelm you. Use cheap sweeping moves for multiple enemies, just make sure your actual target is the one in front center.
As the levels get more difficult, you'll learn quick that Alisa/Raven MUST NOT DIE. That one health pack is a joke, especially on the Nightmare Train level. Pretty much you have to pay attention to all of the items you collect and give yourselves the best stat bonuses. To get my S item achievement I farmed for a bit with ~70%+ item drops on both characters (I seemed to have better luck on Hard mode), which helped me get a nice bunch of A items which in turn helped me complete all of the extra levels.
A lot of it is luck, there were many times when I couldn't believe I won (especially the Nightmare Train). On the other extreme there were many times when I couldn't believe I lost (getting knocked off the ledge is infuriating).
Everyone loves Nancy and Azazel! For Nancy it's either quick charging moves that deal a lot of damage or a ton of quick moves with a lot of dodging. It takes... quite a few tries, but at some point she'll finally give in.
Azazel is again where you can't try to do anything fancy. Spamming short quick moves will kill it quickly, especially if they have a juggling effect. My iron rule was to never try a jumping move, as it counters almost every time with something terrible. It's actually fairly easy to juggle, and any two combo hit will usually make it pause for a second, which allows you to execute the next two combo.
There's of course the cheap trick of setting the battles on easy and one round, which I definitely took advantage of for the gallery and survival mode achievements.
This was actually the toughest for me because I'm so horrible at fighting games, so winning a ranked match was a bit of a pain. Basically I had to play as cheap as possible with a ton of spamming, and by sheer luck I won one ranked match and one player match. After then I only had to fight 5 matches to get the final achievements. Thankfully the online achievements for this game are very few and very non-demanding.
And there you have it, I never touched an Xbox till about a month and a half ago, and this is my first big accomplishment.