What is the easiest and safest way to get rid of very aggressive ground bees? I am not able to mow the lawn or doing any gardening around my flower bed at the front of my house, as these bees will sting and there are many of them.
The two solutions I've used in the past are avoidance and hot soapy water. Where I live at least, wasps use abandoned ground squirrel tunnels, but they use them for one year only. If you can avoid entering the area around their nest for the rest of the season, the problem will go away on its own.
If that isn't a possibility, pour a large bucket of soapy water down the hole after dusk, quickly cover the hole and leave. In my experience, this is as effective as wasp/hornet spray and you don't have to worry about harmful chemicals.
One successful method that I have used is to wait until dusk when the bees are not active, pump a generous amount of wasp/hornet spray into the hole, put a rock over the hole, wait of few days. This worked every time I tried it.