I used Vance AI Anime Upscaler to enlarge some anime images, which some prefer to call waifu images. As it claimed that it uses the best waifu2x algorithms to focus on the enlargement without losing the quality of lines and colors, I have a quite satisfying experience with it. Especially, it allows to upscale anime images by 2x, 4x, 8x, and even up to 16x free online.