Implemented Ended with code 255

I play minecraft from two places, my PC which works fine and my fathers Mac X OS.
If I try to even just launch the game it crashes with code 255, which from what I've gathered means stuff is missing as it normally happens to those who create their own modpacks. Here is what I've tried and how many times:
Force update (3)
Hard force update (2)
Deleting files then reloading them (3)
Tweaking with settings (2)
Redownloading launcher (3)
No matter what this happens:
Process ended with code: 255
Can you help me?

 

I'm assuming your using the MYM launcher. Yes? Could you post the crash log here or with a link from pastebin.

 

Thank you, I had searched for half an hour on if this had already happened yet missed it. Sorry it was late, I wasn't at my father's until recently.