For office, light gaming, etc. the cooler is easily sufficient. However, since the cooler was only designed for up to 65W TDP, you will tend to have worse temperatures/thermal throttling with VERY CPU-heavy applications (CAD, rendering, etc.) and should fall back on an alternative (with the same height, switch to an AiO). Of course, manual OC (voltage reduction, etc.) would be possible to keep the i5 9600K in check a bit or limit the package power to e.g. 65W.