Liquid or gaseous hydrogen (yes, H2 is hydrogen whether gas or liquid)...that is not so much a rocket task as it is a plumbing task. It took an incredible amount of development by NASA to get the Atlas Centaur upper stage to work, and that was around 60 years ago. Entirely new welding techniques had to be developed because H2 will leak through cracks less than one ten-thousandths of an inch wide. Not sure I know of a single amateur who is working with H2.
I've worked with hydrogen gas a little bit in my profession (chem prof, 42 years) and know enough about the subject to Just Say No, nosiree bob, uh-uh. There are lots of easier ways to destroy/incinerate/remove body parts.
If you're a welder by profession, and are able to make top-quality welds in stainless steel...that might be a starting point. Or it might not.
If you mean something else, please elaborate.