Porcō Galliard

In the form of a titan, Jaws fought you.
how can you fight me?! I'm the titan of jaws!
He was in shock.

Driven by anger when he learns that Bertolt Hoover died and his former Titan is being used by Paradis to destroy the Marleyan fleet, Galliard rushed against Eren in a blind rage and oblivious to Pieck's pleas.
This left both Pieck and Zeke more vulnerable to attacks, which was the opening the Survey Corps needs to defeat them afterward. This personality trait also got Galliard ambushed by Mikasa Ackerman, when she realized he will act carelessly once he saw the Paradis Island airship flying above Liberio.
This led to him being mangled and used to destroy the crystal in which Lara Tybur protected herself.
History
Some years before the Paradis Island Operation, Galliard was a leading candidate to inherit the Armored Titan.
He participated in the selection process along other Eldian children. He and his older brother Marcel were chosen to be candidates for Warriors after an extenuating physical test involving running under the rain with military equipment.
After reuniting with the other six possible candidates and receiving the information about the future offensive against Paradis Island, Galliard scolded Reiner Braun as he considered him the only one without a special talent, being only fueled by his love towards Marley and his adulating towards their superiors. After Reiner accused him of being an Eldian spy, Galliard punched him and was stopped by his brother before continuing to their destination; even though Marcel had convinced him to stop the assault, Galliard continued to mock Reiner.
It was eventually decided in the year 843 that Reiner would inherit the power of the Armored Titan; Galliard's brother Marcel was additionally chosen to inherit the power of the Jaw Titan. When the Warriors departed for Paradis Island, Galliard remained behind on the continental mainland.