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The top contenders I have experience with is: -Aesprite. It's paid. It's good. Built solely for pixel art.
Free stuff: -LibreSprite- this is the open version of aesprite before it went paid. I don't know it It's still maintained or updated, but it may suit your needs.
-pixelorama- web based made in the godot engine.
It’s still open for a other 40 hours.
Go here: https://www.gog.com/en/game/tropico_4 then clock the link that says go to giveaway.