Anti-Venom Horrifying Healer

As title states, I’m thinking about building an Anti-Venom deck. But I had a quick question as far as the damage prevention goes. So in the text it says “If damage would be dealt to Anti-Venom prevent that damage” my question is obviously if I block I get dealt damage but what if I attack? Let’s say he’s a 5/5 and I attack my opponent and he blocks with his 2/2. Even though he’s blocking and I’m attacking technically 2 damage is still being dealt to Anti-Venom right? So i can prevent the 2 damage and put 2 +1/+1 counters on it making him a 7/7 then damage happens? I could be wrong which is why im asking for help🤣 thanks in advance!