Top 10 Most Powerful Pokemon off all time ranked 

Yveltal 

Before the introduction of Galerian Moltres in Gen 8, Yveltel was the only Dark-Type Legendary in the series, making it incredibly useful in certain situations.

Reshiram

There are plenty of Dragon-type Legendary Pokémon these days, but when Reshiram was first introduced in Gen 5, there wasn't nearly as much competition.

Solgaleo 

First introduced in Gen 7 games, Solgaleo is a psychic/steel-type legend with high attack and special attack stats.

Zekrom

Like Reshiram, Zechrome boasts one of the series' more distinctive designs, with its completely black appearance making it an incredibly difficult Pokémon to forget.

Xerneas

Due to the recent addition to the franchise, there aren't nearly as many Fairy-type Pokémon as there are the other 17 types.

Palkia 

Palkia's dual typing can sometimes be like a double-edged sword, though it is one of the best in both the water- and dragon-type categories.

Dialga 

Like his fellow Gen 4 veterans, Dialga has been blessed of two kinds.

Lugia 

Although not quite as popular as its fellow gen 2 mascot, Ho-Oh, Lugia is still an incredibly useful Pokémon to have on one's team; Assuming that the players can find one.

Giratina

Whether in its original or modified form, Giratina has an impressive base statue of a total of 680.

Ho-Oh 

Like many of the series' earlier Legendary Pokémon, Ho-Oh scored a base stat total of 680.