So, I download the launcher and download tekkit legends, no problem. When I tell it to play, It will run through the various checks and what-not and the launcher will hide, because it is set to hide when the game starts. After about 30 seconds, the launcher pops up again like nothing happened. I checked the console, turns out the game is crashing on startup. It does this for any modpack, even vanilla minecraft. I am running the latest version of Java 8 64-bit with 2gb ram allocated to the technic launcher. Crash report can be found here. I have found several people with the same problem, but nobody has an answer that works for me.
Edit: It works now, thank you, JaariAtmc!