Percy Jackson and the Olympians Season 1 Ends with Unresolved Threat from Titan Kronos

Despite returning Zeus' stolen thunderbolt, Percy Jackson fails to convince the gods of the impending danger posed by Kronos, leaving the possibility of a future war among the gods.

Percy Jackson and the Olympians Season 1 concludes with Percy Jackson (Walker Scobell), Grover (Aryan Simhadri), and Annabeth (Leah Sava Jeffries) successfully returning Zeus' stolen master thunderbolt, thereby averting a war among the Greek gods.
Percy discovers that his friend Luke (Charlie Bushnell) was the one who stole the bolt for the Titan Kronos (Nick Boraine), who is trying to regain his place in the world.
Percy fails to convince the gods of the threat that Kronos poses, leaving the possibility of a future war among the gods still imminent.
Percy's stepfather Gabe (Timm Sharp) is turned into a statue after opening a package addressed to Percy containing Medusa's head, a possible act of retribution from Poseidon.
The series ends on a cliffhanger with the threat of Kronos still looming and Percy's life being directly linked to the Titan's ability to break free from Tartarus.