There are some Pokemon that COULD kill us, but probably wouldn't. Maybe they're the minority, but they do exist. Besides any Pokemon that can heal with Heal Pulse, plus Xerneas, Tapu-Lele, Chansey, Blissey, the entire Togepi line, the entire Cleffa line.
"As everyone knows, it visits peaceful regions, bringing them gifts of kindness and sweet blessings." - Togekiss Pokedex entry
That, in combatination with Gyarados would actually probably enforce peace.
"It is an extremely vicious and violent POKéMON. When humans begin to fight, it will appear and burn everything to the ground with intensely hot flames." - Gyarados Pokedex entry
All of the above (Gyarados aside.) are helpful; Cleffa's line can all offer you some form of happiness/good luck if you merely see them in the right way!
And even Gyarados isn't completely horrible. Its Mega Form, apparently lost all brain function, except "its destructive instinct to burn everything to cinders.". However:
"Although it obeys its instinctive drive to destroy everything within its reach, it will respond to orders from a Trainer it truly trusts." - Mega Gyarados Pokedex entry.
With even a Pokemon that berserk able to cooperate with a trainer it trusts, I think trainers who can bond well with their Pokemon would have a lot of potential, if they survive.
There's also the possibility of someone making a good wish on Jirachi if we last long enough (Ex: "I wish for everyone who wrongfully died from Pokemon to get to live happy lives as good people".), or Celebi time travelling to somehow help us.
Any Grass-type with plant-healing abilities, like Meganium is, funnily enough, a godsend for us; After using our nukes trying to kill, say, a rampaging Tyranitar or Camerupt, healing plants would be invaluable for replenishing irradiated/dead crops.
It'd be hard, but doable. Delibird & Tropius's food MIGHT help if it's not irradiated. Pokemon like Dragonair might be able to clear out the nuclear winter by controlling the weather. We would also have Absol in some places to warn us of disaster. There are probably other Pokemon with more obvious, dubious or less beneficial ways of helping us. Most Pokemon could help generate energy. Pansage's leaves whisk weariness away, relieve stress, & is good at finding berries from all over, gathers them & is kind enough to share them with friends.
How about we work out what Pokemon would be most beneficial to us in The Real World but with Pokemon? Much more interesting to ponder than "We all die quickly, lol", IMHO.
