Fighter Speed Stinger is one of the dragons that were fighting for the Dragon Hunters the Dragon Fighting arena until Hiccup and the riders set them free.
Fighter Speed Stinger looks like any normal Speed Stinger.
At some point before Stryke Out, the Fighter Speed Stinger was captured and caged in a cave along with a Razorwhip.
When Hiccup and Toothless got trapped in the same cave, the Dragon Hunters took them and the other dragons to the Dragon Fighting arena. However, th Speed Stinger was kept in a different place than the other fighter dragons.
The Dragon Hunters put it to fight with a Triple Stryke, but it lost the battle. He was presumably freed along with the other fighter dragons at the end of the episode.