Suder was a Betazoid but unlike most of his species he seemed not to be empathic. It's possible that this was related to his other personality disorders.
He joined the Maquis in 2370, though his homeworld was not under threat. He worked under Chakotay and was an effective member of the Maquis although he did not engender much affection from his colleagues. They regarded him as too efficient when killing Cardassians and this made them uncomfortable around him. In fact, Suder was using the Maquis as an escape valve for his unnaturally violent nature.
A quick investigation by Tuvok uncovered his crime and he was put under house arrest in his quarters. An experimental Vulcan mind meld by Tuvok was carried out with the aim of helping Suder to control his impulses. While to some extent it was effective, the resulting trauma to the Vulcan's emotional systems resulted in him losing some of his emotional control, becoming dangerous and violent.
Over the next few months, Suder worked with Tuvok to maintain his self control and began to find enjoyment in other activities. He started work on Orchid breeding and eventually became proficient at genetic manipulation of plants. He had plans to use this talent to increase the output of the ship's airponics bay.
This progress cam to a halt when Kazon-Nistrim agent Jal Tierna detonated a biological explosive on Voyager in his quarters. These were adjacent to Suder's and the Betazoid was believed killed. While the ship was taken over by the Kazon, Suder hid in an access conduit and managed to make it to Sickbay where he found The Doctor, who was already planning to retake the ship when Suder arrived. During their sabotage efforts, Suder was forced to kill a Kazon soldier. Despite the Doctor's assurances that he had done the right thing, he succumbed to a panic attack as he had been working so hard to avoid his violent impulses. After the Doctor was deactivated by Seska, Suder was able to sneak in to Engineering and sabotage the secondary phaser coil, causing it to explode when it was activated. He was, however, killed by a Kazon soldier in the process. (VOY : "Basics, Part I", "Basics, Part II")