нафига - why the hell (usually meaning 'why do this', 'no good to do it like this', 'what's the purpose of doing it in this way' etc.), and it's slightly rude, not a taboo

noone gives a eff - different options depending on the degree of rudeness

1) "всем плевать" (not very rude, can be used speaking to your boss) - lit, everyone spits on it; an option is "всем начхать" (a bit less common) - lit., everyone sneezes on it (the full version is "всем плевать на это", "всем наплевать на это", "всем начхать на это", "они плевать на это хотели", "им всем плевать на это" i think there are different variations possible)

2) "всем насрать" - this one is rude, and not to be used speaking to your boss (lit,. everyone sh*ts on it), similar longer extended phrases are possible here

3) the rudest taboo version is "всем пох..", "им всем пох.." - which exactly means 'they don't give a f... about it'