>「まったく…こうなるとどいつもこいつも、殺{ころ}したほうが、世{よ}の中{なか}の為{ため}に**なり**奴{やつ}ばかりに見{み}えてくる。」

「どいつもこいつも」 is a despicable and slovenly way of saying "***everybody***", so it is often translated as "***every man jack***", "***f***wits***", "***all those bastards***", etc.

「ばかり」 in this context means "***all (of them)***" as it is used in pair with 「どいつもこいつも」.

Regarding the 「なり」 part, as @snailplane pointed out, it would need to be 「なる」 for the sentence to make sense.

>"Damn! Given the situation, (just about) every f***er is starting to look like one that would only serve the world better if killed."