1. Gogmazios for me, I tried in every single way to avoid spoilers on what it looked like and fighting it for the first time was a surprise.
2. I prefer entirely new monsters, feels like the "new" ones are more unique.
3. Favorite final boss(and favorite monster in the series so far) is Osutogaroa, I seriously love everything about this monster.
4. Least favorite is definitely Ukanlos. No matter which MH game I play I always have terrible luck trying to get his rare drops... The first time I fought him years ago in MHFU I kinda expected more than just an icy Akantor with a swimming attack.
5. I just hope Capcom can keep making new final bosses for future MH games. The final boss monsters are always some of the coolest in my opinion.
6. I'd say Rusted Kusha. With the huge buildup I was expecting an epic and challenging battle but it was just a tutorial for the battlequarters. Sure Rusted Kusha could be fought later in G rank but it was a shame that he didn't keep the amazing theme.
7. I don't care too much but a bit of buildup is always nice.