Alright, so I've had tons and tons of problems already. Mostly about the minecraft launcher not working. I did lots of researching and finally found that I needed to use the Jar launcher instead of the native launcher.
After that, when I tried to start the game, java gave some errors which I fixed by going to "Edit Profile" and unchecking the JVM Arguments box (I have no idea why it works, I just tried it out).
When I click the play button, minecraft starts and starts constructing mods. After some time of waiting the game just closes and returns to "Game Output" tab on the launcher.
Here is the report the game gives (.txt file):
Can anyone help me with this? I have no idea what's going on and frankly I'm fed up with all the problems I'm getting just to play modded minecraft.
Oh and I should add, I'm trying to use EthosLab's modpack.