I'm seeing people say that I Jedi could beat a Space Marine, and because I do not like fake news, I'd like to share this, also because WH40K is really cool.
So, the thing is, an average Jedi is an honorary peacekeeper, enhanced with the powers of the Force and tasked with maintaining its balance. They are brave, generous, each one uniquely adept, and their weapons themselves are meant not to be the most effective, but to represent honour.
An average Space Marine is a brutal warrior, uplifted from human bonds to that of a demigod, tasked with enforcing the will of the (God-)Emperor across the galaxy. They have no fear, they have no restraint, and their form is one to be truly terrified of to any and all of the xenos or the traitor.