Killing ASE with a SIGKILL is obviously not a good idea but you can run out of other options.
Data-loss can and will happen because no checkpoint will be given to the database.

Should it unavoidable you need to check some actions before starting such as the shared memory segments and files.
The shared memory files are located under the $SYBASE/$SYBASE_ASE directory with the SERVER_NAME.krg file name. The sybase process should be able to read and write in this file.

Shared memory segments also need to be cleaned up. These can be identified with ipcs | grep sybase and ipcrm -M <KEY>