Shotguns are overpowered, here is a video I made on the topic. Don't worry, it's good quality! :-)
https://www.youtube.com/watch?v=IezsjPE5j_A&list=UUz4FYUUd7D--ymw3JvGIhYg
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Shotguns are pretty much instakill in any game, just don't let them get close to you. Kinda simple to avoid getting killed by them as they're close range.