Finally reinstalled macOS Sierra, but now I get a kernel panic
A kernel panic is nothing more than a software crash. A bit like when an application quits for no apparent reason, except in this case, it brings down the entire system, since the kernel is the heart of the operating system. It looks like you weren't done with the installation, because it appears to be trying to continue the installation, but can't for some reason. I'd boot into recovery and reinstall from there by holding down commandrwhile booting.