The battery life on my new iPhone 7 is HORRIBLE. What the ****?

Did you restore this device from the backup of an old device? Go to Settings>Battery and see what app is using the highest percentage of your battery. More than likely, and this happens a great deal with all of the iOS updates, you have a process or app that is stuck attempting to perform a function. User troubleshooting is restart, reset, restore from backup, restore to factory; testing after each step. Sometimes in the update process, especially I've seen if attempting this OTA, this can occur. Generally the restart or reset will fix it, but if you have to restore from backup, make sure you take a current one. If you have to move on to restore to factory, then test it for a period of time before attempting to add any additional content back. You should see an improvement.

Restart your iPhone, iPad, or iPod touch - Apple Support

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Use iTunes on your Mac or PC to restore your iPhone, iPad, or iPod to factory settings - Apple Support

Just came back from the Apple store. Apps did not download, phone very very hot and battery draining fast. I entered the store around 13:00 and at 80% battery. They asked me to erase and start again. After 1 hour i was left with a 1% battery and a phone that was burning hot; my hands were itching from touching it. Apple refused to change phone. All normal according to them. I've used a 3 a 4s a 5 and a 6. Never had a similar issue. iphone 7 big flop. Don't waste your money. Wait for something better tested.