they are both tough but Venom is smarter and sneakier..... he can turn practically invisible and the symbiote spreads impacts out so that most super-guys punches don't hurt too much, i doubt the Scorpions acid would be very useful but if Venom tried to grab his tail he'd receive a few thousand volts for his troubles...... it would be a good fight but i think Venom would win
^Venom doesn't have a spider-sense....he has the symbiote which acts like a gigantic eyeball.
The symbiote can "see" enemies coming from behind him because the symbiote will warn him of the immenent threat. It's just like a Spider-sense, but weaker in some areas and stronger in others.
The symbiote is going to have a rough time "warning" Eddie of a bullet flying at him....so it's bad in that instance. But it's good because the symbiote will catch the bullet meaning Venom doesn't have to dodge it anyways.
All that to say Venom would take this win.
Scorpion remains a weak character with a weak flaw and that's the taunting. That alone provides a means to his downfall. He'll get pissed off and start spraying acid everywhere without thinking and BAM!!!!
Venom lands a lethal blow that sends dumb dumb to the nearest psych/intensive care unit