He played multiple memorable roles in Star Trek. The roles were touching and sympathetic characterizations.
1. The Next Generation - He played a conscientious Romulan admiral manipulated by sinister forces.
2. The Next Generation - He portrayed Worf's son Alexander as an adult who returns to his past to help his father understand and accept his son's gentle nature for what it is and the glorious future he would help initiate.
3. Deep Space Nine - The scientist who studied and taught Odo under a repressive regime.
4. Voyager - The scientist who destroyed Neelix's homeworld and wanted to redeem himself.