Not to discourage further information, but this was posted previously:

https://www.reddit.com/r/AskHistorians/comments/1yj43r/hitlers_accent_when_speaking_german/

The gist of it is, it wasn't really strong, but there were traces (for example he rolled his r's in the Austro-Bavarian style rather than swallowing them as in Hochdeutsch).

The only recording of Hitler speaking casually rather than making a speech is the Mannerheim Tapes, but it may not be an entirely true reflection as he may have been modulating his accent for the benefit of a non-native speaker.

He may have laid it on a bit thicker when wanting to present himself as being a "man of the people" or when throwing a hissy fit, but the commenter who says this provides no source or evidence so...

The answer to this is a bit more difficult than you would imagine. In short, no, at least not like Gordon Brown.

We have had previous questions about this here and here.

The basic gist is that we have very little recordings of him speaking conversationally and as an Austrian, I think you can hear some dialectic influences of southern German dialect varieties in the "r"s and some other words but not very noticeable - at least not to the extent that it would constitute a heavy accent.