BTMT/Season 1

Season 1
Season 1 started with Return of Vilgax, Part 1 and ended with The Spookiest Finale, Part 3. In the beginning, it revolved around stopping Vilgax and Aggregor from getting the Potis Altiare, but towards the end, it changed to stopping Albedo and Zs'Skayr.

Episodes 1-2: Return of Vilgax (Parts 1 and 2)
Pilot. Vilgax escapes from Albedo's Omnitrix, and starts a quest to get the Potis Altiare. To make it all worse, Aggregor comes with the same purpose. With Azmuth revealing a new Ultimatrix function to Ben, Ben needs the Potis Altiare more than both of them.

Episode 3: Ben? Who's Ben?
During a fight with the Vreedles, Ben crashes on Appoplexia and gets amnesia!

Episode 4: Back to the Future!
Ben and Co. travel to the future again for a repaired Potis Altiare Piece. But Future Ben is really Albedo!

Episodes 5-6: Dawn of the Squid (Parts 1 and 2)
Vilgax got the full Potis Altiare, but it ended up on Ben. Eventually, Azmuth gives Ben the new Omnitrix, Gwen the Mannamatrix, and Kevin the Metalmatrix. But Vilgax, with lots of power, shattered Taedenite Kevin! Now, they must stop Vilgax from sucking the universe into the Nothing Dimension.

Episode 7: He's Back! (Part 1)
Aggregor returns, captured by Darkstar, but when they absorb each other's powers, they fuse together, only Aggregor's mind easily overwhelmes Darkstar's. After absorbing Kevin's powers and Gwen altogether, he goes after Ben's Ultimate Alien!

Episode 8: Ultimate Aggregor... Again (Part 2)
After absorbing the Ultimate Alien, Aggregor gets a new form. He looks like the Ultimate Alien, just with a modified look. After that, the defeated gang must look to [http://pffanon.wikia.com/wiki/New_Super_Flynn-Fletcher_Bros! another series] to stop Aggregor once and for all!

Episode 9: The Rise and Fall of Albedo
Albedo's back, and is impersonating Ben now that his form isn't damaged anymore.

Episode 10: Zs'Skayr?
Ghostfreak escapes from the Omnitrix and fuses with Ship. Now revealing his true name, Zs'Skayr, he travels to Vilgaxia in "spaceship mode." The gang goes there, too, but gets shot down onto Probity's planet (from Simple).

Episodes 11-13: The Spookiest Finale (Parts 1, 2, and 3)
Season Finale. Ghostfreak has posessed Albedo and wants revenge on Ben and Co.