Complex sentence: Judge Martin Sinfield is a fictional supporting character and antagonist in the "Judge Dredd" comic strip in "2000 AD", most notably in the story "Tour of Duty" (2009--10).
Split into simpler sentences: Judge Martin Sinfield is a fictional supporting character and antagonist in the "Judge Dredd" comic strip in "2000 AD". He is a main character in the story "Tour of Duty" (2009--10).