Guadalpin in Marbella.
We were at the pool at 10am one morning, and it was deserted. Our kids were just playing in the pool, as kids do, not really shouting just splashing around, when the manager came out and asked if we would be quieter as some of the guests were trying to sleep.
Large dish of candy at the front desk, the kids would take one whenever they walked past, maybe 2-3 times a day, eventually they were told not to take any more!
This was during school holidays, and was supposedly a family friendly resort.
I am seriously wishing that going forward my worst hotel experiences are no worse than this! Never fear, I won't be so lucky.