After 42 is the level 50 skill Infuriate. You learn this via your Warrior job quests.
Underneath your MSQ tracker which tells you the next MSQ to do is a smaller text that tells you the next job-specific quest to do. Like the big icon you can click on the little text to map your way there.

However, this may be the case where you've already learned it but you are on Marauder not Warrior.
Please go to your equipment and in the last slot on the right ensure you have Soul of the Warrior equipped. You won't see WAR-specific skills if you're not a WAR but only a MRD!