Lightroom CC on iPad. Free, and good enough for a casual like me. The only thing I miss is the ability to duplicate photos, but that's it. I've edited photos on it (12.9") exclusively for the past two months, and really enjoyed it. So much so, with the new iPadOS (which I'm downloading right now) and the ability to plug in external drives and with the introduction of a file system, I sold my MacBook Pro.