UQ Holder 140

Double Boss of Justice end is the best end, friend.

It's the good timeline. Touta doesn't exist so she ending with the one similar to him makes sense.

Touta is going to sacrifice himself.

Does this mean Negi has to call Eva mommy?

Negima's timeline Negi managed to save his father as shown here with the help of Asuna. This Asuna is the one that wakes up late and everyone is already dead (even Negi it seems) but still in the the same "good" timeline, and she's brought back to the past to help save Nagi at the last moment.
This saved Nagi is the one Eva gets married to, the one from Negima's timeline, the good ending. Touta does not exists in any point of this timeline, since he was never created.

Touta's timeline's Nagi isn't saved and was probably killed by Negi (as the Mage of the Beginning is now possessing him) because in their timeline Asura doesn't wake up in time to the last boss fight nor is brought back to the past, so without her White power they can't save Nagi. Then Touta is created as a replacement for Asuna to save Negi instead. In this timeline only (UQ's) Touta meets early Kitty because of Fat Witch's power, but in this timeline the fight against Nagi is already past and gone, so there's no Nagi anymore for her to marry. She then gets attached to Negi, the reason why she rejects Touta.

tldr: she married negima's nagi.

waitaminute

Did Nagi remarry between series?

Why is Chamo showing Touta shit from a timeline that is unrelated to him?

This. He was denying it forever.

To find a way to save Negi.

Becouse Touta is a fuse of Negi and Asuna

We see that Negi combined his ME power with Asunas power to defeat Ialda without killing the host.

So now Touta knows that he needs to train both those powers in order to combine them and try save Negi with it just like how he saved Nagi in the good timeline.