There are places where we have had food issues, or service issues, or both at the same time, but I generally will give a place a second (or third) chance before writing it off completely. That said, there are two restaurants that you could not pay me to eat at again.
1. Wolfgang Puck's cafe. On multiple meals, we have experienced overcooked burgers, raw burgers, burnt pizzas, raw pizzas, but never properly cooked food. The restaurant has been less than ideally cleaned when we have visited also, and service has always been mediocre. I've never tried the upstairs restaurant...maybe some day.
2. Restaurant San Angel, Mexico pavillion, Epcot. Caveat: our experience here is from about 10 years ago, and I am sure it is different now. However, our one time eating here is forever seared into our brains as a "must-not-repeat," as follows:
At the time, I was a vegetarian, and there was nothing on the menu for that diet. Before being seated, we inquired with the host, who said they could accommodate us. The waiter confirmed that they could prepare the enchiladas with just cheese, no chicken. I said that was fine. The meals came out, and my enchiladas contained chicken, so I sent them back. The chef came out of the kitchen, pointed at me, and started yelling at the top of his lungs! It was very disturbing to us, to say the least, and probably to everyone around us as well. The waiters had to push the chef, still yelling, back into the kitchen.
After this lovely scene, they brought out my entree again. It was obviously the same enchiladas they had brought out before, just with the chicken pushed out. Except for the piece that they left right in the middle of the dish.
Needless to say, we have not been back. May your experience vary!