Do rpm -q kernel-core to get the list of installed kernels. Then dnf remove the ones you don't want. Edit /etc/dnf/dnf.conf and add exclude=kernel* to the [main] section at the top. Hopefully the 4.7 kernel will work better when it's available soon.
If you edit the grub boot entry and remove quiet and rhgb from the kernel command line, you might be able to get more info on what's happening. Can you get a picture of the kernel panic? I expect the kernel developers would like to know about it.