Veigar is one of the 3 champs I play. Here’s how you beat him:
If his E is down, he’s completely defenseless. He has 0 mobility (an increasing problem with mobility creep), so running him down is effective.
He has very little damage before level 6, and his spells are generally too expensive to just be spamming, so before level 6 he should be a minimal threat. Even at level 6 he’s not so scary unless you have 1/3 HP or less.
Ward. Veigar’s E combined with an enemy gank WILL be very dangerous, so make sure you’re warding.
Veigar thrives in extended fights where he can keep back peddling safely (if he can’t just obliterate the enemies). His big weakness is being dived and cc’d or pulled/caught by someone like blitz or thresh. Generally he’s fucked in that scenario unless he has flash and E and some bonus HP.
As an adc, you are still a threat to him even inside the cage if you weren’t stunned, as you can still auto and dodge his spells. Just don’t touch the walls, the cage only lasts 3 seconds.
Though it isn’t bot lane, divers like J4 also cause HUGE problems for him.