There is a way to have both old Varus and new Varus

https://i.imgur.com/bmXZ7P2.jpg

The answer is surprisingly simple, have Val and Kai be Val and Kai but have the new Darkin Varus be old Varus.

To those that don't know, old Varus's lore involved him being a protector of a dark power held in a temple, he was both a husband and father as well. Because of these two different obligations, that between his family and being a guardian, when Noxus attacked his village he had to choose between protecting the temple or his family, he chose the temple and regretted that decision when he found his village destroyed and its people, including his family, killed. He then chose to release the power in the temple and use it to hunt and kill Noxians until it eventually fully corrupted himself as both vengeance for what was done to his family and people and as atonement for making what he saw as, the wrong choice.

The new lore of Val and Kai can't really be changed, it is too new, has too many resources put behind it, and deals with a politically sensitive issue. However, Varus, the actual new character with the name Varus, has not been explored much yet, there is still potential and hope for the fans of the old Varus there.

Why not make Darkin Varus's past follow that of the old human Varus? Why not instead of just being a torturer and savage being for seemingly no reason, they make it so he's like that because his past is like old Varus? Perhaps Darkin Varus was not always hateful of humans? It says in the new lore that he was part of the second wave of Darkin that came to Runeterra, what if instead of coming just to slaughter, he initially came with calls of peace?

His group of Darkin could have come with the intent to live alongside the races and peoples of Runeterra and had established a village or city of Darkin, in which also was his family. Then it could be that later, thanks to fear of what the Darkin had done in the past and their fearsome appearance, a coalition of humans attacked the Darkin village/city, and destroyed much of it, killing many of the Darkin, including all of Varus's family except for his sister. Darkin Varus then vows to kill all Runeterrans for what they had done and dedicates himself fully to becoming a true monster because it was his "foolish" belief that the Darkin could live in peace with the Runeterrans that led to his family being killed.

So while this would not be completely the same as old Varus, this would at least be able to keep the over all themes of old Varus, that of regret, hate, and revenge, in the new Varus lore.

Edit: Perhaps a better story would be Varus coming with the initial Darkin who weren't initially out for carnage and slaughter on Runeterra, at this time the Darkin would have even given things to the Runeterrans like the knowledge of blood magic. But then the incident with betrayal happened and after an initial attempt to fight the Runeterrans, the Darkin left and then returned with a stronger second force with a real focus on killing and destruction.