In a 2017 livestream where he plays PlayerUnknown's Battlegrounds, there is a point where PewDiePie gets angry at a player and starts aggressively using profanity against them - and unknowingly to himself he calls the player a "Nigger". As you would expect, this gained a lot of controversy despite PewDiePie realizing his mistake after he said the slur but he did apologize for it, admitting that he sees using slurs for fun as being immature and tasteless.
As of recent, his scripted videos are made more for younger audiences and don't have as much profanity than his older videos, with stronger words bleeped out. This is mainly due to YouTube's demonetization guidelines. His streams still have excessive swearing, however.
One of his music videos is called "B**ch Lasagna".
Religious profanities are frequently used throughout his videos, which includes some uses of "goddamn" and "Jesus Christ".
Should kids watch? Yes, but be aware of the bad language used a whole ton.
Lots and lots of uses for the F-Word and the S-word.
Fuck' or 'motherfucker', and other milder language are said often. Sometimes, 70 times for a twenty minutes long video.
There is one use of "cunt", but it is quite hard to hear and it is only mentioned in two or three videos. One time, he loudly said " You spiky, fucking cunt!", while playing "Cat Mario 4".