Ben finally beats Vilgax, but with a huge cost. All of the people Ben loves is dead, Gwen, Kevin, Julie, his parents, Grandpa Max, there all dead. With Ben all alone with Ship at his side, he becomes depressed until he is transported to another world where he gains another family, will he learn to trust and be happy again or will the past come to haunt him.
I got this idea from another story, but I forgot their username thing but credits to them. It has the same themes as them but different plot and worded differently.
Ben 10 x justice league
Ben Tennyson hasn't been on earth for several years after he learns that he has been lied to his entire life. After 4 years of being off planet he comes home to find things are very different. Upon his arrival to earth he meets a young women by the name Kara Danvers. Together they decide to travel across the U.S. where they meet old and new friends. At the same time an old enemy plots against earth. Will Ben Tennyson rise to the occasion. Is it hero time once again?