Yes A bug type for example...Nincada with leech life you can easily K.O any grass type (as long as its at a decent level!) But If you have a grass type like Treeko and go against Wurmple well if you use absorb on wurmple it will be "not very effective." So Yes Bug type moves Are VERY strong against grass type.
Water Pokemon with water attacks or Grass Pokemon with Grass attacks
Water-type Pokemon are weak against Electric and Grass-type attacks.
Water-type Pokemon are weak against Electric and Grass-type attacks.
Grass type Pokemon are strong against Water, Ground and Rock.
Flying, Poison, Bug, Fire, and Ice type moves are strong against a Grass type Pokemon.
In my opinion, Ludicolo is the best Grass Pokemon, because the Water/Grass combo is strong or neutral to most attacks.
A Water Pokemon's weaknesses are Electric and Grass. Basically any type of Pokemon can beat a water Pokemon if it's strong enough, but Electric and Grass attacks do 2X damage against Water types. Water types also only take half damage from Fire, Ice, Steel, and Water attacks, so those wouldn't be the best ones to use. Water attacks do half damage to Dragon, Grass, and Water Pokemon. Its strengths are against Fire, Ground, and Rock.
water/grass
When attacking, Infernape has the advantage over Grass, Ice, Rock and Steel-type Pokemon. When defending, Infernape has strong resistance to Fire, Grass, Ice, Dark, Steel and bug attacks, but is particularly weak against Water, Flying, Ground and Psychic attacks.
Ice-type Pokemon are resistant to only Ice-type attacks. In offense, Ice-type Pokemon can do 2x the damage to Grass, Ground, Flying, and Dragon-type Pokemon.
Bug-type Pokemon are strong against Grass, Fighting, and Ground-type moves.
Water and Grass attacks are super effective against Onix.