I am sorry, normally I don't do this but what the hell are you talking about
enel777 ? Witcher is my jam. I read, watched and played everything even barely connected to the lore. I dare to say I know most if not everything there is about the whole shebang sooo I just must call your bs out.
1st of all, you are talking about games or rather one particular game. 2nd - Witcher games aren't canon at least according to the creator, Mr Sapkowski. I am not saying games are bad because it's clearly not true, I love them very much but everything you base your knowledge on is just what CDPR came up with on their own. In books there is not a lot about Vampires so clearly they had to do something to even tell this story. Soooo because it is a game you had to fight a boss and you had to be able to defeat him to move forward, (yes defeating a higher vampire in combat is possible, Regis was defeated but I don't want to spoil too much). That's interesting and exciting but the truth is you cannot kill higher vampires. Nothing and no one can EXCEPT another higher vampire. Thing is, they won't do it because there are so few of them left and because they don't care about humans, ok maybe except Regis. Normally no Witcher would even try to fight higher vampire because its a suicide and because they are so rare. Mostly they just avoid any contact.
Something like that more or less does really happen but Geralt almost loses that fight and we are only talking about 1 Bruxa here. If not for Nivellen, Geralt would die there. So NO, in reality I don't think Geralt would be able to defeat the higher Vampire.