Force an Aggregator image to be responsive(?)

I have Aggregator set up and working fine, pulling in RSS feeds. While everything “works”, I have encountered an issue that I would like to fix/make better. My site is all responsive, and everything else adjusts to work with the screen size of the device, however, one of the RSS feeds has this HUGE (like 4k size, currently non-responsive) header image with it. As this code changes each time they update the feed, I obviously can’t just update the code. Is there some way to force images via RSS to be responsive?

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