The problem here seems to be that the encrypted file was never properly encrypted fully – as you note, the encrypted file is much too small. Even though AxCrypt does perform compression, a .avi-file is already compressed and will not compress at all or very little. So the expected size of the encrypted file would be in the same range as the original file, i.e. 599Mb.
So, something must have happened to interrupt the encryption process. In this case, the original file should not have been wiped either. Is this perhaps a file that was encrypted some time ago, so whatever happened happened so long ago you don’t remember the details?
In any case – there’s no way to decrypt data that is simply not there. Sorry.