Darren Cross, the evil "genius" from the first Ant-Man, had the cunning plan to re-create Hank Pym's technology to harness Pym Particles so he could mass-produce his own Ant-Man suits to sell to terrorists. He kept failing to make the shrinking technology work and would instead turn cute little lambs into bubbling piles of goo. Side note: if you work for Cross Technological Enterprises and didn't realise that your CEO is an evil dickhead after watching him repeatedly turn lambs into puss, you're a dumbarse and I'm glad your place of employment was destroyed!
He then uses it on a bloke that he had a minor disagreement with and reduces the guy to a bloody glob of jizz that can easily be disposed of with quick wipe of a spank-kerchief. Here's an idea, idiot, why don't you sell the raygun that turns people into snot to Hydra instead of a suit that makes them tiny? Hydra would jump at the chance to have an army of agents armed with goop guns. What easier way for them to achieve Red Skull and Hitler's final solution?*
Sure, it could be argued that Cross had gone a bit nuts due to his excessive exposure to the Pym Particles and he only cared about figuring out the secret of his former mentor. That said, you're a crap business man if you can't see the marketability of your accidentally created disintegration gun.
*We at Empire Ink in no way endorse the racist agendas of genocidal super-villains
Unprotected Exposure to Pym Particles Make you a Crazy Person
As touched upon in the previous section, it's established in the first Ant-Man film that if you get repeated direct exposure to Pym Particles, it erodes your brain. In the comic, it's the reason why Hank Pym beats his wife. Whilst it seems to make Hank Pym a bit of a grumpy tosser he clearly wants no harm to come to his wife in the film version. Grumpy ol' Hank makes it clear to Scott that the suit is needed to stop this brain damage.
In the sequel, Ant-Man Sr, Ant-Man Jr, and Wasp Jr are tooling about in a miniaturised van. What happened to needing the suits to avoid brain rot? You can't tell me that an automobile (with the windows down no less) can provide the necessary protection. Maybe Disney wants to include spousal abuse in their next Ant-Man flick but I hope not: I like my good fun comicbook films to be largely devoid of domestic violence.
Regardless of Size, Mass stays the Same
The reason that an ant sized man can knock out a regular man is that he retains the mass of Paul Rudd sized man. Ignoring the fact that Ant-Man's density would probably create a black hole, this rule only seems to apply when a human is ant sized.
Carrying around a pocket sized tank would be pretty bloody challenging if it also retained the mass of a full sized tank. That keyring in the first film should be as difficult to lift a Thor's hammer. The second film sees our heroes dragging a building around like a suitcase...A FUCKING BUILDING! Good luck with that, morons. I guess hyper-intelligent characters shouldn't be written by simpletons but hey, it works for the show Big Bang Theory.