We're not talking about that specific guardian, are we? The OP was "a" guardian. On a side note, can any guardian do that? Any Spartan can do what Chief did. Any Spartan II that is. Besides, your point was that chief couldn't kill Crota or Atheon, right? Who gives a damn? A guardian couldn't take on the Insurrectionists, Covenant, Flood, or the Didact- the closest thing to a god in the Halo universe that there is- by themselves either could they?