Yuusha Kei ni Shosu: Choubatsu Yuusha 9004-tai Keimu Kiroku

"Hero" is the worst punishment in the world.
For those convicted of heinous crimes, they are sentenced to become a “Hero" and forced to enter the mandatory military service in the war against the Demon Lords. These convicts are not even allowed to die—if killed, they will be resurrected to fight another day.
Hero Xylo Forbartz, former head of the Order of the Holy Knights, leads a penal unit of deplorables fighting on the front lines. It’s in these direst of circumstances that he meets Teoritta, one of the world’s the strongest weapons.
"When every last enemy has been defeated, you are to shower me with praise and pat my head."
In order to survive and to take revenge on those who wronged him, he makes a pact with the goddess and launches headfirst into a maelstrom of war and intrigue.
(Source: KADOKAWA Anime)