The relationship between Kanan and former Sith Lord Maul is a villainous pairing between the two adversaries. Kanan did not trust Maul even though Ezra insisted the former Sith was on their side, and only tolerated Maul when Ahsoka (reluctantly) agreed they could use Maul's aid.
But once Maul made his true intentions known, that he intended to take Ezra away from him, he struck Kanan with his saber, blinding him, and would have killed him had Ahsoka not defended him. Kanan found an old Temple Guard mask to cover his ruined eyes and stood up to face the deceiver again. Maul arrogantly underestimated Kanan, believing killing him would be quick and easy.
But Kanan remembered his Jedi training, trusted his senses amplified by the Force, and not only bested Maul but thwarted his plans by sending him falling over the edge of the sith temple terrace.
Somehow, Maul learned of Kanan's former identity, Caleb Dume, and after blackmailing Kanan and Ezra for the Sith Holocron in exchange for the lives of the Ghost crew, he split the two up in order to attempt to kill Kanan again (but Kanan was able to survive Maul's attempt).
Maul saw Kanan as an obstacle between him and Ezra (who he considers his own apprentice) but twice underestimated him.