I understand you're now very desperated because you've tried every possible method that may fix your MacBook not turning on issue, including booting into macOS (Internet)Recovery Mode, resetting SMC and NVRAM/PRAM, but your Mac still refused to turn on normally.
Then reinstalling a fresh Mac operating system could be your last resort to fix the issue. It is easy to reinstall macOS because Mac will instruct you how to do it all the way in Recovery Mode. However, if you're worried about reinstalling macOS will wipe all your data on your Mac, you should recover your data from the unbootable Mac first.
Since your MacBook Pro failed to transfer data to your iMac using Target Disk Mode, you can only use data recovery software to have a try. Not all the data recovery software in the market has the ability to retrieve files from a MacBook that won't boot, you need to get one that supports it. iBoysoft Data Recovery for Mac is able to recover data from an unbootable Mac in an easy way.
Besides, iBoysoft Data Recovery for Mac can be launched in macOS Recovery mode through Terminal without the need to create a bootable drive on another Mac.
Now, do the following to learn how to recover data from a Mac that won't turn on:
- Start your MacBook in Mac Recovery Mode using the below steps. Turn on your Mac and immediately press down Command + Option + R keyboard keys together (not regular Command + R). Hold them until you see a spinning globe on your screen.
- Choose a network for your Mac and make your Mac connected to the Internet all the time.
- Open Terminal from the Utilities drop-down menu. Type the following command in Terminal and press Return to launch iBoysoft Data Recovery.sh <(curl http://boot.iboysoft.com/boot.sh)
- After launching iBoysoft Data Recovery, follow the wizard to scan data from Mac hard drive and recover data.
Once all your needed data has been recovered from the unbootable Mac, give your Mac a new clean macOS. Then your MacBook Pro should boot up normally.