Minecraft keeps crashing

Put the summary of the bug you're having here

What I expected to happen was...:
I expected to Launch MC successfully - I choose realms and it crashes almost every time.

What actually happened was...:
I choose realms and it crashes almost every time.

Steps to Reproduce:
1. Launch MC
2. Click "Play"
3. Choose "Realms"
4. Click "Play"
Very frustrating