Two others were sentenced to life in prison and nine others to various prison terms.
The death-row convict, Saifullah, is at large while the life-term convicts, Mamun and Ziarul Islam, were present in court to hear the verdict.
The other convicts are Md Zulfiker, Abu Hasan, Abdul Malek, Abdus Salam, Rabbani, Bellal Hossain, Zaman, Rahim and Piklu.
A total of 23 people were acquitted of charges.
A clash took place between two rival groups of villagers based on a dispute over distributing water from a deep tube-well pump on farm land in Bakra village in Ashashuni Upazila in 2014.
According to the case dossier, Habibullah Sarder, an honours student from Satkhira Government College, was killed in the clash, said additional public prosecutor Tapan Kumar Das.
Police pressed charges against 35 people in the case filed over the incident.
Among them, three suspects had absconded, according to Das.