There are many different kinds of Pokemon in Pokemon GO in terms of shape, size, color, and rarity. However, not every Pokemon is so easy for every trainer to catch once they find them.
Much like in the main series of Pokemon games, Pokemon GO has different capture rates and odds for each Pokemon. Common Pokemon like Caterpie or Pidgey will be way easier for players to catch than Mewtwo or Giratina.
The most elusive Pokemon in Pokemon GO
There are a lot of factors that go into making Pokemon hard to catch. For instance, capture rate is one factor, and how often the Pokemon moves around on the screen is another. Pokemon with a high chance of fleeing or with a higher CP are also difficult to acquire.
Tyranitar, Dragonite, or Charizard are going to be some of the hardest Pokemon to catch in Pokemon GO due to their rarity, combat power, and because they are fully evolved. There are also Legendary Pokemon found in raid battles that are extremely hard to catch. Thankfully, Niantic makes these Pokemon easier to catch if they have ties to a current event. Still, however, these are not guaranteed captures after every battle.
Pokemon like Zubat and Yanma are notoriously challenging for trainers to catch in Pokemon GO due to just how often they move around the screen. They are worth the trouble, however, as they are very valuable Pokemon. When they fully evolve into Crobat and Yanmega, they are very powerful. This means that players have to catch a lot of these Pokemon, and they will waste a lot of pokeballs by missing the target.
Pokemon with high flee rates can also be a challenge for many trainers to obtain in Pokemon GO. While Pokemon like Caterpie are ubiquitous and not hard to catch, their high flee rate can make them devastating for some trainers who are just one candy away from a Butterfree, but the only Caterpie nearby will not stay in the ball. The Pokemon with the highest flee rate, however, is Abra. While other Pokemon with a high flee rate only have a 20% chance of doing so in Pokemon GO, Abra has a base flee rate of 99%. Missing the first attempt at catching Abra will almost always result in it fleeing.
The most difficult Pokemon for trainers to catch in Pokemon GO with all factors considered, along with the effort and work it takes even to get a chance to catch one in the first place, would be Ho-Oh. Ho-Oh is a Legendary Pokemon players could battle in 5-Star Raids. After Ho-Oh has been defeated, players would get a chance to catch Ho-Oh in Premier Balls. Premier Balls are also the only Pokeball permitted to catch any Pokemon fought in a Raid Battle, so Great or Ultra balls cannot be used to increase a Pokemon's capture rate. Without berries, Ho-Oh only has a 2% catch rate and requires battling in a 5-Star Raid with each attempt making Ho-Oh the hardest Pokemon to catch in Pokemon GO.