Heat oil in a Dutch oven or heavy pot over medium heat; cook and stir onion until softened and beginning to brown, 10 to 15 minutes. Add garlic to onion; cook and stir until fragrant, about 1 minute.
Stir kale and water into onion mixture. Cover Dutch oven and cook until kale is tender, about 30 minutes; season with salt and pepper. Drizzle balsamic vinegar over kale and caramelized onions and sprinkle almonds over the top.
