There is no such thing as a "minimum" CPU because every game is different. We cannot generalize games, and we cannot generalize CPUs, because every game is programmed differently. A Pentium will suit you on some games, but not many. It'll bottleneck on a lot. The I5-4690K is two generations old, and with the I5-6600K I don't see a viable reasont o get the 4690K anymore, since Skylake, DDR4, and compatible mothebroard have had many price adjustments since their release.
If you're asking for my opinion on the minimum, I would say grab an I5-6500 with an H110 motherboard.