My #1 suspect is a slug — likely a very large mature one. When I bring my avo’s indoors for the winter, they begin to get freshly chewed leaves like this along the tender leaf edges near the top. Eventually I find them, but they are very good at hiding. I’m not too worried since indoors, numbers are limited to only the stowaways, but outdoors, you may want to use a trap or organic bait/poison like Sluggo.
But try tipping the container (if it’s in a container) over and look underneath ... also under any other objects like rocks in the vicinity.
The browned leaves may have been sunburned.
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