Normally the dot matches any character except newlines.
So if .* isn’t working, set the “dot matches newlines, too” option (or use (?s).*).
If you’re using JavaScript, which doesn’t have a “dotall” option, try [sS]*. This means “match any number of characters that are either whitespace or non-whitespace” – effectively “match any string”.
Another option that only works for JavaScript (and is not recognized by any other regex flavor) is [^]* which also matches any string. But [sS]* seems to be more widely used, perhaps because it’s more portable.
(.*?) matches anything – I’ve been using it for years.