Complex sentence: Beef (Buford Wilson) is a fictional character from Marvel Comics, a mutant from the Hellions group created as the antithesis to the X-Men's junior team of mutants, the New Mutants.
Split into simpler sentences: Beef (Buford Wilson) is a fictional character appearing in American comic books published by Marvel Comics. The character is usually depicted as a mutant from the Hellions group created as the antithesis to the X-Men's junior team of mutants, the New Mutants.