Delete all files whose filenames contain a particular string?

Use find to recursively find and delete files with "text" in their names:

find -type f -name '*text*' -delete

You might also want run find -type f -name '*text*' (without the -delete) before that to make sure you won't delete any files you didn't intend to delete.

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In fact, you can place wildcards anywhere in the search string, so -name '12_angry_men_lone_holdout-*.jpg' might be more suitable in your case.

If they are in the same folder use * wildcard to achieve that:

rm *text*

Where text is string that filename contains.