Answer 1

By power it would be Frenzy Plant at 150, then Leaf Storm at 140. They're both special attacks. Check out the link below for the full list of grass moves!

http://pokemondb.net/move-type/grass

Answer 2

frenzy plant and leafstorm but they also have very big drawbacks

Answer 3

Frenzy plant is the strongest, but only stage two starter pokemon can learn it and they have to like you enough.

Comments

acutally all grass starter last evolved form pokemon can learn frenzy plant look it up

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I looked it up and only stage two pokemon can learn them.

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In Diamond/Pearl, they say in the game that only grass starters at stage two can learn Frenzy Plant.