to get no rebound you would be looking at a improper oil level in the shock and it will not function properly.
You should have some rebound. Depending on the shock it should be about 1/4 to 1/6th the extended length.
The reason ther is rebound is becasue there is a small pocket of air that is trapped in the end (under the bladder) to allow for the expansion of the oil level as the piston compresses.
Air being Compressable vs oil that is not will give and keep the oil from gettin gair bubbles.
If you did not install the bladder and over filled shock it would not be able to compress properly and risk blowing the cap off the end.
and too little will introduce inconsistant resistance witht he introduction of air bubbles.
I hope this was not too long