Rival Battle: Seviper vs. Zangoose!

Since Pokémon III generation this two pokemon were known rivals. Who in your opinion is the winner and why?

Seviper, poison tail.

Zangoose is a normal type and has no strengths, of course it can learn dark and bug type moves and has the ability Immunity and Hidden ability Toxic Boost, Serviper is poison type who can poison and learn dark moves with Ability Shed Skin and Hidden Ability . Zangoose's stats are 73, 115, 60, 60, 60, 90 in order of HP, Attack, Defence, SP. Attack, SP. Defence, and Speed, whilw Serviper is 73, 100, 60, 100, 60, 65. Hard decision... I'll say... Serviper cause I want to poison things

Zangoose for the win, love squirrels/mongoose's (It looks like a squirrel :D) and he is just absolutely epic man.

Zangoose. 'Nuff said.

Zangoose

Zangoose is only weak to Fighting; Seviper has more.

Seviper. Because I said so.

Actually, let me refine my answer. It would purely come down to who raised the pokemon and how. Though naturally it would go to the pokemon with even the slightest advantage, pokemon natures were introduced in Gen III and affected the strongest and weakest stats of a pokemon. TMs can also be brought in as part of the movesets. 

Let's examine possibilities of a 6th Gen Zangoose from Black & White 2.

Zangoose has the ability Immunity, meaning it can't be poisoned. Even if it's given the Hidden Ability, Toxic Boost, it will have it's attack increased by 50% while poisoned. It can learn Sword Dance, one of the best attack stat boosting moves. It can be taught TMs 39 and 80, Rock Tomb and Rock Slide respectively. It can also learn a few powerful fighting type moves like Close Combat and the EGG move Final Gambit.

Now Serviper. 

Serviper's abilities, Shed Skin and it's Hidden Ability, Infiltrator, are poor match-ups against Zangoose. Though it has a resistance to Fighting Type moves like Final Gambit and Close Combat, Zangoose receives a bonus STAB when using Normal Type moves. The move Work Up, taught via TM, boosts Attack and Special Attack. This alone can prove dangerous against any pokemon that isn't a steel, rock, or ghost. 

Serviper also has a good ace. Gastro Acid can remove the effect of another pokemon's ability, meaning Zangoose would be open to the poison status. It also has the EGG Move Final Gambit. 

In the end, both pokemon have their own positives and negatives, but I still give it to Zangoose. He's a normal type, maximize friendship, teach him return and work up. Work up once or twice, then use return... So much fun.

I have to agree with C. Also, Zangoose has this cool red scratch which looks like a scar, unlike Seviper, which looks like half of Seviper's tail was just peeled.

I voted for Seviper, because goin' by show logic, its attack always have about that 5% chance of poison,