Thank you, Bobbert.
Certainly, they are all good to describe that from the point of view of an external observer, but I think I'm facing here another untranslatable cultural thing. Expressions in Spanish tend to describe defects as an internal process, hence you can use "ser un negado" to describe a person that may try something and come short, in spite of their powerful will. That's why you can say "soy un negado para esto" without falling into the winner-loser dialectics so popular in the USA.
Maybe my problem is I parse every instance of English indicative as if it is Spanish indicative and give too much credit and weight to what is said in English. The English verbal system is more elastic. In "ser un negado", the use of the only substantive verb means I have to take full responsibility for what I say. That is also true for English in some way, that why I often suggest the use of
E-Prime in opinion forums, which existence I learnt from fellow forum user wrholt.