Usage of word here

I heard the sentence off of a radio broadcast show or something(don't remember exactly),
"As a matter of fact, being either extremely realistic or unrealistic each has its very deadly consequences, and as a person who has suffered from both ends, I will definitely say one should absolutely think twice before taking any action, make sure that s/he's not jumping headlong into something that will not pay off or will eventually kill him/herself while being at it."


I'm not quiet positive about my idea on this,
but I think that the "deadly" here's bit too intensive, or even illogical,
because if that person suffered from "deadly" consequences,
that would probably mean that s/he have died twice according to the context...
But then it leaves the question, which word should be used here to indicate a meaning of extreme devastation?
All I can think of is "fatal", but don't you think that's almost equivalent in meaning to the word "deadly"?