Views over Osaka, and the city lit up
Observation decks, open-air viewpoints, and bridges and buildings lit up after dark. Each place is here because its own listing says so. Hours and fees change; check each place's site.
Observation decks
Their listings mention an observation deck (展望台).
Open-air viewpoints
A hill, a temple stage and a park whose listings say you can see out over the city or the sea.
Lit up at night
Their listings say they are lit up after dark, and when, where they give a season.
Listed in 大阪府 観光施設一覧 / 大阪市 観光施設一覧 (CC BY 4.0). Photo credits are on the terms page.