The only batch was Mr. Beer (back before they were bought by Coopers) that I dumped. So less than 2 gals. I persevered through gushers and other things. I didn't want to be accused of "alcohol abuse".
I dumped a few probably 3. But one that I dumped I missed about 6 bottles, it was an irish stout. I found them about 6 months later mixed in with some other bottles so I threw them in the fridge and tasted them after about a week. They were actually really good. Bad mistake on my part.
Now I also made a few that I would not serve to anybody because of how bad I thought they were but was able to manage to drink them myself.