My favourite boss fights from the last decade are definitely primarily from Bloodborne. I am generally not a fan of bosses at all in games, actually (with some rare exceptions). I often feel like they just get in the way of the game's flow for me.

But I feel like Bloodborne's bosses were a true "event". They were regularly challenging, sure, but I think they were also generally pretty interesting from a lore and design perspective. A good example is Rom the Vacuous Spider. That boss is pretty unique in terms of the encounter design itself (and the setting), but the impact Rom has on the broader world after you defeat her is kind of mindblowing. I think that's what makes her so memorable for me.

Outside of that, I struggle to remember a boss that really stood out to me in a very strong way. One possible recent exception is "Jeff" from Half-Life: Alyx. You could argue - perhaps tenuously - that the encounter with Jeff is one long, drawn-out boss "fight". It's very much a series of puzzle encounters, but each one is among the most unique I've ever seen in a video game. For these reasons too, Jeff stands out to me as a great example of how boss design can be effectively handled in VR games.