“Partial” icon in a comparison table

Personally, I would drop the icon and go with just the “Partial” text.

I would also make this a clickable link (visually al least), so it is more obvious that you can find out more information (rather than having to hover).

However, if I had to choose an icon I would go with some kind of “half filled” shape. Perhaps a square or circle depending on the rest of your design style.

Very quick example (excuse the rough edges):

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