Who are you a paladin of that allows you to wield a sentient sword of that much evil energy. If your God and faith is OK with it then use it. Its way overpowerd for your level. If your God is anything but evil it should not allow you to use it. But your playing in a homebew world i assume. So who cares about balance?

People are allowed to play as they like. There is no reason to try and gatekeep or shame someone. 

While that sword is extremely powerful by most standards, it is part of someone's game. It is ok at their table. They aren't *lesser* for having things they enjoy, even if you don't like the balance of it, or object to a paladin using it. Without knowing what is considered moral in the setting we can't actually comment on whether a god should be ok with a follower using it.

The item is based on the Stormlight Archive series. Im not going to expound on that, in case the op hasn't read the series and is playing in a setting for the first time, but essentially: if the setting is essentially the world of Stormlight Archive, the gods are probably ok with it.

He asked what we thought. Why are you attacking  me. He said it was to powerful i agreed. If its allowed so be it. My questions were valid he never examined his paladins convictions so I was asking  still dont know if they considered that.