Marissa was Wrath fonte of feeding, but he never mated with her. Everybody thinks that Wrath and Marissa were mated but in fact they weren't even though at the beginning she loved him she only gave him her blood, so he would be able to survive. He never slept with her or loved her to begin with, Beth was the female that brought these feeling out of him for the fist time. With Marissa the words "MINE" and the bonded male feeling never came out, with Beth they came out as soon as he meet her just has bonded male should when they find their mate. Besides Wrath and Marissa were never officially mated on front of the Scribe Virgin hence the point he didn't amor her. But with Beth, Wrath asked the Scribe Virgin the permission to mate Beth, hence he got her name on his back. And if he and Beth have kids their names would also be carved on his back blood signifying that they're blood from his blood.
Because Marissa and Wrath never really had a ceremony of their union. Plus, he always thought that Marissa was to good and delicate for him. He wasn't really serious. She was just promised to him por his parents. They were just not right for one another.
Since Wrath thumbed his nose on the whole ascension thing it would follow that he didn't feel he was worthy to have happiness in his life when Marissa was promised to him. She represented all his failures as an unworthy son and male because he didn't save his 'rents (in his mind) so he didn't want to take his rightful place as the King. Remember the conversation between him and D, he's always felt unworthy, and Marissa being the eptomine of all that was worthy and perfect was like a slap in his face.