So the hornwort I had in my tank died and shed their needles alllll over my tank. My question is how do I get it out! I got most of out it with a syphon but some of it remains on the bottom stuck in the gravel and to my driftwood.
Keep doing your best at getting it out. You ought to be able to get the vast majority out over a few successive cleanings. What you don't get is going to decompose and become an additional contribution to the bioload.
I don't think you should drain your aquarium to get them out. It would be best to try and vacuum them out as much as possible. 50 needles might lend a significant amount of ammonia to the system, not to mention other toxins and pathogens that may be present as a result of the decomposition. But, no, I wouldn't advise draining and starting over.