One of the required qualities of the best herbicide for wild violet is it should be in the systemic class. Systemic herbicides work when it gets absorbed by the plants through their leaves and stems and also roots. Even the rhizomes can die with systemic herbicides. But since you’re trying to kill only the wild violet in the lawn and not the grass, you should choose the selective types that will kill only the broadleaf plants.
There are 2 things to remember when choosing a herbicide for wild violet in lawn:
It should be systemic and not just a contact herbicide.
It should be more effective as a postemergence herbicide.
How to get rid of wild violet more effectively is during its postemergence cycle when the seeds are beginning to sprout which is their most vulnerable stage. So if you’re wanting to know what herbicides are best, choose those that contain any of the following: 2,4-D, MCPP, Dicamba, triclopyr, fluroxypryr or flumioxazin. These chemical ingredients are made to be systemic and can kill many types of broadleaf weeds including the Henbit, Purple deadnettle, and Creeping charlie.
There are a lot of products that carry any of these chemicals and you can do your research and buy a product online but it should be from a legitimate seller or store. Or to be sure, visit your horticultural supply store in your area so you can personally inquire about what you need.
Also, if you want a specific product that is already proven to be an effective best herbicide for wild violet and other broadleaf weeds, check Roundup for Lawns product. However, you should be aware of how to use this product and know the best time when to apply it.