202.) Be aggressive. Slam that bitch across the room with F+2,1,2 and shadow kick her to death in the corner. She's pretty damn aggressive, so just try to trap her and beat the crap out of her.
239.) I spammed a combo (2,1,2) and chained in some hair whips, and her cartwheel. It's difficult because Kitana wouldn't stop square wave punching.
281.) Once again, Kitana is flighty, so I teleport kicked her and then whacked her with a combo or two (B+1,4 or 4,2) and repeated.
293.) Figure out a good 3 hit combo or so, and I like to abuse his (enhanced) dive kick.
300.) Losing several times, I think, drops the difficulty slightly. Abusing crossovers/projectiles (somewhat) will help with Goro/Kintaro/Kahn, but you need to be defensive with Mileena. Make her use a punishable special, and then beat the crap out of her.

The others, a friend did for me before I punched a hole in my wall.
Hope some of that helped.
If you're really struggling, go into practice mode, and recreate the challenge somewhat with the same opponent, and set the difficulty up....maybe that will help you find your way.

185: I'm sorry, but I've skipped this one

202: Sindel's fucking aggressive, so combo her ass or keep spamming her shadow kick.

210: Again, I've skipped this one

293: This worked for me, but I was keep Air kicking his face

The other ones I had my friend do. Sorry about that, hope this helps somewhat 281: with Mileena and Kitana, teleport kick her then follow up with a combo(and repeat)cuz Kitana is once again Aggressive and flighty

281) Block like hell, and link your favourite kombos to it. NEVER let her hit you, CPU Kitana can do some pretty cheap and unfair kombos that almost kill you after the first juggle has been triggered.. 293) Like above, airkick-spam his face off.

Ok, I will deal with the easiest one first (no joke), 269; Just get some distance (full screen if possible) and spam the living shit out of your gun. Repeat 3 times and the only thing to worry about is the hammer, so keep a close eye and jump it, then back to spam. That is it.

275; Get comfy with Ermac's bnb combo ( lift, jump kick, tele-punch.force push). Don't try and get fancy because he will hit you with that spinning fist thing of his. Land aforementioned combo and follow it up with a fireball. Be carefull of a new Goro coming in with a xray, I was caught by that plenty (a new one seems to have a random amount of meter) Good time to punish is when he does his jump forward stomp, just jump towards him and bring the pain.

210: Sorry but this one there is no trick to, it should be easy to you from playing ladder. Kintaro is literally the easiest guy to fight in this game. Just keep your distance, wait for a taunt oterwise jump back and punch at the highest point if he does his teleport. Hits him every time.

251; I found the CPU is very stupid when it comes to blocking upward fireballs, so use them wisely. Key in this fight=remember that you can heal yourself with throws, so use plenty on first two and go against Shao with good health. Then same procedure, get full stage distance and spam your normal horizontal fireballs. Avoid hammer.

300; It's the only one which gets easier every time, so just pick someone your good with and bam. Mileena is the biggest concern here. Very aggresive, so block lots and punish.

I have done them all but was a while ago so I cannot give advice on the rest. (tilt the world in particular, I still have no idea how they work, just beat the shit out of them) A general tip when fighting 3 people, use your xray first chance you get. You will have it charged again by the lasy guy, so you get to use it twice. I always wanted to try save it for the end.

185 - If you can make it to Kintaro, you're in the clear. Stay on the ground against Sheeva (the AI loves using the anti-air grab) and Goro can be beaten with crossovers. Kintaro is cake, as always, even for Baraka.

202 - Pressure, pressure, pressure.

210 - I don't see what's so hard about this one unless you suck with both characters. Crossovers and short combos will do the job here.

239 - Learn a 3 or 4 hitter and spam it.

244 - This is one of those challenges that forces you to switch out frequently, right? I like using Kitana for as long as I can and switching to Jade for quick breathers, but do whatever you feel most comfortable with.

251 - If you can't flawless Baraka or come close to it, you might as well restart this challenge. Sindel is going to whoop your ass, guaranteed, the goal is getting to Kahn with at least 1/2 a life bar in tow.

269 - Gun. Enhance if possible.

275 - Not too hard as long as you don't get caught by any of Goro's more devastating attacks. Employ a rope a dope strategy here, tends to work for me.

281 - I really have no advice for this one. Don't blindly throw attacks because you will get punished, but constantly trying to punish doesn't work because Kitana is pretty safe, so you'll be eating block damage most of the time. Just try to land some big combos when you can.

293 - You're limited to high hits here, so go for freezes and try to jump in on Sektor, even though he isn't really safe to do it against.

300 - Pick who you're best with and keep trying until you win.

I didn't skip any so I went through a lot crap. Alright baraka has a great upercut so try and get in and that as much as often.that shift the tower thing was really hard first of all stay ducking and blocking whenyour not attacking spam the crap out of your boomerang and shadow kick and when you build up supermeter use it on the boomerang.don't even attack kintaro just focus on shao khan it dosen't matter how much of either one you hit they rotate out pretty often.as sindel get her in a corner and spam that cart wheel thing.don't remember 244. This ones really hard as shang tsung try the combos that hit low a lot and just grab the first 2 when you get hurt. Spam the gun blast non-stop and just jump over the hammer I f he raises his arm to through a spear just shoot anyway it will stop him 90 percent of tha time. Ermac jump punch, upercut constantly.spam mileenas sai through from long distance. Whatever one punch or combo that hits the head the fastest and spam it . Use smoke and spam his smoke bomb and teleport punches and time itr right with shao khans spear through and hammer through.there you go.

I have 5 uncompleted challenges I dont remember all of them, but the army of Shao Kahn and Goro Yeah I skipped that bullshit.
Good Luck though