For one KFC chicken breast there are 180 calories per KFC chicken breast as well as 6g fat, and 31g protein.
KFC chicken is not the healthiest and can be fattening if you need to watch your calorie intake but eating 1 or 2 KFC chicken breasts is not gonna make you fat or at least not too much fat as long as you continue to exercise if you want to keep your weight off.
I order my family a bucket of KFC chicken once or twice per week when I can afford it and I eat 2 of those chicken breasts with the bucket of chicken and I haven't gained anymore weight.
But I also exercise and eat more healthy food on the other days as well to prevent myself from getting out of shape and prevent weight gain and health issues.
As long as you stay active, eat other healthy foods etc then you should not gain much if any weight when eating KFC chicken in moderation.