Took down Great Wroggi and Rathian. Rathian in particular reminded me of the dangers of poison.
And then I went on and decided to take down Lagi. And holy crap was it a close call. For one thing I forgot just how dangerous his berserk mode can be underwater. More importantly, though, I forgot to restock up my whetstones before fighting him (and I'm using Dual Blades). After an intense battle of me carting twice and then fighting him for probably about half an hour, he slinks back to his cave, and I realize I no longer have any whetstones. My blade goes down to yellow, and then becomes dull, and I'm thinking to myself "crap, crap, crap, CRAP!" At this point the only way I can damage him seems to be to hit his (broken) chest with demon mode blades. Just when it seems about time for my blades to degrade further, he FINALLY goes down, and I'm just straight up rejoicing.
Man, this kind of stuff is what makes this game so damn awesome.