We present a grain boundary (GB) solute drag model in regular solution alloys. The model accounts for solute-solute interactions in both the bulk and GBs and captures effects such as monolayer, multilayer, and asymmetrical segregation. Our analysis shows that deviations from ideal solution thermodynamics play a paramount role, in which solute drag is shown to scale with solute-solute interaction parameters. Further, it is found that the asymmetry in GB segregation introduces an additional component to solute drag. A universal solute drag-GB velocity relation is proposed and used to explain recent experimental observations of sluggish grain growth in a wide range of engineering alloys.