How to fix part going out of control with linear velocity

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#1

(https://gyazo.com/6734d79ba9c982d0697bb98aa003c45c)
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https://gyazo.com/6734d79ba9c982d0697bb98aa003c45c

#2

im trying to get the sword to just point straight and go straight but for some reason it just goes out of control