Q.how do I kill lace bugs?
They are all over my sunflowers. I tried soapy water and general pesticide, but they keep coming back.

How often have you sprayed? Spray the plant with insecticidal soap or neem oil at two-week intervals to control newly hatched lace bugs. Thorough coverage of the plant with the insecticidal soap/neem oil is critical.
The following article will help you:
https://www.gardeningknowhow.com/plant-problems/pests/insects/what-are-lace-bugs.htm