Sounds like you are going to have to let it drain out until it turns off. Then leave it off an charge it, but only charge it a little. Once it has a little bit of a charge, then turn it on in "Safe Mode" and see if it loads up OK. You will have limited access in this mode, but if it works and loads, then you may well have a bad app, virus, malware, etc. on the phone that you will have to remove before it will work correctly.
If, however, it won't turn back on in "Safe Mode" either, then it may be a hardware issue.
To get into "Safe Mode" please do the following.
1. First turn off the phone.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.