There is no shortage of cute Pokémon to appear in the Pokémon games through the decades of releases we have seen. Even with that being said, bunnies are about as cute of a creature as you will come across. Here is how you can evolve your Buneary into Lopunny in Pokémon Legends: Arceus.
To evolve Buneary into Lopunny in Pokémon Legends: Arceus, you will need to raise the friendship level of your bunny Pokémon. To do this, you generally will just need to use your Buneary a lot.
First, make sure they are present a lot in battles and do not faint before you win. If they do get low on health, use berries and potions to heal them. The more battles against trainers and wild Pokémon you win with Buneary on the field, the more they trust you and have their friendship level raise.
Additionally, Pokémon friendship levels can be raised by feeding them EXP Candies. You get these most commonly from completing Requests. For another small boost, use Buneary to collect resources you see in the wild like plants, fruits, and stones.
If you are curious how your friendship is growing, you can talk to Belamy in front of the Pokémon Pastures area in Jubilife Village. Once you hit the proper level, you will get a small message that your Buneary can evolve the next time they evolve.