Its not great.....Its pixelated and jumpy....but a good try none the less.

Plus, the lifebars are set wrong, you might wanna move those to the correct proper place. No shadows. And why no sound effects? I'm pretty sure you could've found some decent death screams.

for first animation its great, great sounds 3/5

I'm hearing sounds? Unless he just added them in.

Very jumpy.
One piece of advice before even going into the animation is for hosting it.
Find somewhere that'l let you actual embed it into a webpage - otherwise, it resizes to the window and we have no idea of the original resolution you used.
(400 x 254 pixels is default for MK on MAME btw).
The original may not be pixelated, but as it's being resized for us, this may be why it looks it.

Stage is a bit of a mess, in particular the floor and the ground underneath it really don't match. For simplicity, why not grab the wasteland? The backround animation in that is so small you could just use a still image and it would look like the game.

Lifebars and stuff, just take a screenshot from the game and snatch em out of that .

For animating MK sprites (or any really), careful where positining the next one. The easiest way to do this is to look at the feet. Make sure the feet line up with the frame before (use onion skins or just go back and forward one frame until it looks right).
You're going to need a whole lot more sprites than what you have for a smoother animation.

As for the idea, well, it ain't great but it'l do as an effective decap. But instead of making him leap all the way across the screen, make him start a little closer. I know the idea of having him jump across the screen is cool, but animation wise, it doesn't look cool .

More blood! And more parts coming off of the head.

Transparencies - the finish him text has a black background. Im sure everybody noticed that but I thought i'd say it anyway, lol. Use gif or png formats to remove unwanted background colours.

Liu Kang wins text should flash blue and white, but eventually stop on white.

Shadows would be a nice touch, but don't worry about them too much. When you get to know flash quite well, they're a cinch!

Just generally it needs more care and time spent on it. More frames at a faster frame rate will make it flow more smoothly. But, as you can imagine, now with few frames and a fairly fast framerate things are jumpy and quick!

P.S. jus curious, where you studying at uni? I'm doing computer animation in portsmouth atm, lol.

Could use some work, but it's good for your first try at animation.