There are quite a few quests in The Witcher 3. In fact: there are 309 in total. These are my top 30 favourites.
The dramatic penultimate quest of the base game – racing to find Ciri at the ancient tower of Tor Gvalch’ca.
The final boss battle of the base game, with Eredin – the leader of The Wild Hunt. Bear in mind that The Witcher 3 has been out for five years (at this point in time), but I’ll still warn you about “spoilers”…
The dramatic final battle with The Wild Hunt – or at least the first part of it – and a fight with Caranthir, who summons Ice Elementals to protect himself (that I just ignore).