Mid-2010 Macbook Pro won't boot after trying to install macOS Sierra
Try to remove the corrupted 'prelinked kernel' first, then rebuild the kextcache.

From the Recovery HD (putting your own volume's name instead of "Macintosh\ HD") try those three commands in Terminal in succession (pressing 'enter' after each): 

rm -f /Volumes/Macintosh\ HD/System/Library/PrelinkedKernels/prelinkedkernel 
touch /Volumes/Macintosh\ HD/System/Library/Extensions 
kextcache -u /Volumes/Macintosh\ HD 


See also:

man kextcache