To me, only the Zombies have attacks which render you completely helpless.
@tristkiss I have to agree with you. You Engineer Sonic Grenades which is usually a vanquish sentence, Imp's gravity grenade which is usually a vanquish sentence, Super Brainz twister (though unintended probably) stopping you from doing much, Zombie stink cloud which can hinder your aiming long enough to vanquish you and then there is the Scientist which when close to you, you are helpless as you are already vanquished.
All the plants got is a puny Citron Shield which a good player can destroy quickly, Rose's abilities in which the enemy can still escape and attack as a goat as well as a time snare which will not stop them shooting, Chomper Goop which also does not stop them shooting. Well, Cacti can put walls up though enemies can simply find a way around it. Maybe it is justified with all the explosives at the plant's disposal (blame Crazy Dave) as well as several defensive traps such as the Chili Bean Bomb, Potato Mine, Spikeweeds, Well, it is not much though they are usually set and ready as a defensive mechanism while the zombies are normally quick effects.
This is the problem as in GW1, the plants are supposed to defend while zombies attack which caused GW2 to still have the same defensive set while having to go offensive as well. This is why the zombies just make the plants seem completely helpless, plants needs more offensive abilities/stats while the zombies are completely offensive. All the plants got for offensive is Kernel Corn, Peashooter and maybe a Citron while the zombies have the entire 7 class zombie cast with a bonus Imp who could be considered a two-in-one!