Radovid is descendant of Bloody Falka (so no surprise him getting mad, as all her descendants did)... he is the man from her prophecy, she made at the stake - destroyer of the worlds from her blood... so his "new" direction is exactly the direction he should have... its perfectly with the book lore - Phillipa killed him, saving all, becoming Phillipa the Saint...
again something already mentioned by Sapkowski in the books.. he also mentioned 1272 as a year of the Witch Hunt btw...
and they handled him well. If you chose to save Triss, it only changes single thing - he let the conclave be, but controlled them, while he hunted down all sorceresses of the Lodge. Later he just supported Witch hunters (originally, Witch Hunters pretended to be independent, you can read about them in a book - Sword for Witches - only admitting background support from Radovid) in their mission to hunt down all mages, even those under conclave (once they served their purpose and helped to eliminate those dangerous sorceresses like Shille de Tancerville (if alive) or Margueritta)... His goal was always wiping out all sorceresses... because he hated Phillipa and what she represented..
I think people idealized him because of W2, where he was presented as a leader with reason, completely forgetting he was behind whole Salamandra (giving them up only when Aldersberg started not listening his orders and following own agenda) and Civil war in Vizima initiated by Order of the Flaming Rose... he wanted to get rid of Foltest in W1 (and taking Temeria via Adda (if alive), so Letho and Lodge just practically made him a favor in W2 when they killed him off...
so, yeah, lore vise, standoff between him and Phillipa was supposed to happen, as it is mentioned in Sapkowski books. So whenever you participated on his murder, or not, he ends up being dead.. only difference is how much more suffering on other people he is capable inflicting - with winning the war against Nilfgaard, he would cause a lot more damage, yet still being killed by Phillipa in the end... hmm, now that im thinking about it, maybe that is actually the cannon ending.. otherwise, Phillipa would not be called the Saint, if she killed him before he started to wiping out others... ordinary folks would not realize how big favor Phillipa did for them by killing him.... (seems like he will live in my next play-through just for a heck of it - Emreis is supposed to be replaced by Voorhis anyway)
(sorry for all those edits.. it took time to sum up all i had in my mind
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