You can see them in the gallery section

Trophy	How to unlock
Beaten Dry Bones	Beat Dry Bones 5 times
Beaten Hammer Bro	Beat Hammer Bro 5 times
Beaten Kamek	Beat Kamek 5 Times
Beaten Piranha Plant	Beat Piranha Plant 4 times
Bomb Seed	Beat Piranha Plant 3 times
Bowser's MegaMorph Belt	Beat Bowser once
Delicious Durian	Beat Dry Bones twice
Dry Bones's Bone	Beat Dry Bones 4 times
Electromagnetic Generator	Beat Bowser twice
Enchanted Bookcase	Beat Kamek twice
Hammer Bro's Hammer	Beat Hammer Bro 4 times
Jagged Leaf	Beat Piranha Plant once
Kamek's Blue Dictionary	Beat Kamek 4 times
Kamek's Brown Book	Beat Kamek 3 times
Magic Switch	Beat Dry Bones 3 times
Toadette's Chair	Beat Hammer Bro once
Toadette's Piano	Beat Hammer Bro twice
Toadette's Timpano	Beat Hammer Bro 3 times
Winner's Ballon	Beat Piranha Plant twice
Winner's Pen	Beat Kamek once
Yummy Lychee	Beat Dry Bones once