Pretty much all aquatic species larger than the orca are relatively peaceful and do not harass other species (eg, baleen whales, sperm whales, whale sharks, basking sharks). It's not merely a size thing. Orcas, in fact, tend to harass these larger species.

Humpback whales will even go so far as to protect other mammals from orcas.

> For six and a half hours, the humpbacks slashed at the killer whales with their flippers and tails. And despite thick swarms of krill spotted nearby—a favorite food for humpbacks—the giants did not abandon their vigil.

> It’s not clear why the humpbacks would risk injury and waste so much energy protecting an entirely different species. What is clear is that this was not an isolated incident. In the last 62 years, there have been 115 interactions recorded between humpback whales and killer whales, according to a study published in July in the journal Marine Mammal Science.

"Why Humpback Whales Protect Other Animals From Killer Whales"

https://www.nationalgeographic.com/news/2016/08/humpback-wha...

https://onlinelibrary.wiley.com/doi/full/10.1111/mms.12343?c...

Between species? (Some) kids may have occasionally blown up toads, if movies from the 80s are to be believed. But hurting any mammal or bird without a good reason earns you a trip to the psychologist (and police station if old enough). With animals, there obviously is a lot aggression. But I don't think "bullying" is necessarily the right term. It seems more like either predator/pray behaviour or fights to establish social hierarchy.

The latter obviously comes close to one definition of bullying. But bullying as you explain it, i. e. "because I can", seems rare. Which is also what evolution would suggest, since getting into useless fights is bound be net-negative: even if chances of winning are overwhelming, there is always some risk. Plus it's a waste of energy.

As a test I would suggest looking at solitary, herbivore animals with few natural competitors. Here's a capybara: https://qph.fs.quoracdn.net/main-qimg-b1822fb258d0d6a4ce01db...