We know where Agony and Riot's names came from, but what of their powers? They don't tend to display acid-spitting or hammer-forming in the comics, so is it just some fanwank? Surprisingly, no.
The Life Foundation first appeared in Amazing Spider-Man #298, a corporate survivalist group obsessed with making it through what they saw as impending nuclear war. In Venom's first limited series, Lethal Protector, one of the Life Foundation's members used his own company to harvest offspring from the symbiote, forming a super-powered security force. In Venom: Lethal Protector #5, the nameless Life Foundation symbiotes are fighting Spider-Man.
As Lasher and Scream hold Spidey's arms, Phage moves to impale him. Thinking quickly, he swings the two holding onto his arms together, managing to knock all three opponents out. On the next page, one of the two remaining symbiotes flings bits of itself (not spit) at Spidey that begin to sizzle where they splatter against the wall, and then one of them pounds the wall as Spider-Man leaps out of the way. Both these attacks come from off-panel, but it's a small leap to assume one attack came from each enemy, not both from one. And since the only color in either of those shots was a little bit of grey in the hammer, fans assigned that to Riot and the acid to Agony.
(One page later, when all the symbiotes punch Eddie Brock at once, the grey one is again using a big square mallet.)
So honestly, that is the full extent of the "Agony uses acid, Riot uses blunt instruments" thing: three panels across two pages in one issue. It's not much, but now we know.