Deathclaw is one of the toughest enemies you will face in the Fallout 4's wasteland, especially at the highest levels of difficulty, so it's good for you to follow our tips in order to beat him without wasting too much time in ineffective attacks.
Once you have put in a nuclear reactor and got power armor, and took a minigun, go forward and you will be on the roof: you can jump from it, then you will have to face raiders. Kill them and you will meet the first deathclaw, although if you prefer you can stay on the roof and attack it from there.
Attack with the minigun until you have ammo to execute those attacks, then it should remain with about 30% of health. You can now take an ordinary gun to finish it from the roof or launch a couple of grenades/molotov if you have them and it is close enough for you to take it out.
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