Ando's primary power is as you ave noticed to 'boost supers' powers, this is known as Supercharging. The effect this has on non-superpowered individuals is never explained in detail, but has a deleterious effect, injuring them.
The shows creators call it 'sidekick juice':
“Was Ando's ability, augmenting others' powers, motivated by his status as the show's perennial sidekick?”
Sure was. We’ve said a lot, especially here in the BTE, that powers are directly linked to people’s emotional needs. So our perennial sidekick got exactly what he needed: sidekick juice. But after what we saw Ando do to Hiro in the future, there might be more to that red lightning than just power enhancement – more like a sidekick to the groin.
It's not unusual for supers to have multiple powers though, or to have powers with multiple effects. What I think happens is the electricity-like energy that a super-powered individual would absorb usefully just wracks their system instead.
Ando has also used it to crack the combination on an electronic keypad:
And 'unscrambled' Hiro's brain so he can use his powers:
As such I'd guess that his main power is the ultra-fine manipulation of electrical signals. It's possible this control is fine enough to unlock other powers, not boost them. However this theory doesn't hold against the 'hormones' theory behind peoples powers in Heroes. Nothing is well defined enough to give a definitive answer.