So... Many people have the (Launch4J: Nonexistent javaruntime environment or the run time is corrupted. The system could not find the path specified.)
This is... Frustrating, to say the least. I could not play for about 3 weeks. Then, I messed around and saw what was wrong. I tried the Launcher.jar in the game files and.. it worked! Minecraft Launcher loaded, could play FINE. Joined servers, chatted, nothing wrong now. So here's how.
Go into "My Computer" files or "This PC". Look for Local Disk (C:) or OS (C:) in win10. Navigate to the "Users" folder. Choose the one that minecraft is installed on. You should see a file titled ".minecraft". Open up! Inside, search for a launcher.jar file. Run it. It should load perfectly.
TADA! No more frustrations. Have fun! AND THE BEST PART: NO RE-INSTALLATION OF ANYTHING!