Complex sentence: He returned however, to depicting high-rises towards the end of the decade, and this culminated in his production of the arguably definitive work of his career- "A Triptych for Mark" (1991-1992).
Split into simpler sentences: He returned however, to depicting high-rises towards the end of the decade. This return to his iconic subject matter culminated in the arguably definitive work of his career- "A Triptych for Mark" (1991-1992).