Unobtainium is the hardest. got wiki page for it. scarce to impossible to find on earth. the few that we got went to design high grade full body armor equipped with an AI. this one is dubbed the best body armor human yet to make to date.

Also it is widely documented with video and audio of it in outer space in one of the stars few thousand lightyears away called pandora.

It a good thing we have google. do your homework. its on the net and on wiki. obviously this can be trusted. I have faith in the internet.