Cook bacon in a large nonstick skillet over medium-high heat, stirring often, until crisp, 2 to 3 minutes. Reduce heat to medium, add onion and cook, stirring, until softened, about 2 minutes. Add chard and pepper; cook, stirring, until wilted, 1 to 2 minutes. Add beans and coarsely mash; stir to combine. Remove from heat.