Translation:In this case, to reach unit is difficult.
One dictionary gives some of the meanings of "unidade" as: "1 unity: a) the number one. b) oneness, singleness. c) totality. d) uniformity, accord. e) harmony, concord. 2 union ...."
My suggestion for a translation would be"In this case, reaching unitY is difficult". This is fairly literal and does not sound quite natural in English, but I think it gives the meaning accurately
I might as well weigh in on this. In English the word unit mostly refers to a concrete thing, not an abstract concept. The only non-singular unit would be a group of soldiers. So my take on 'unidade' was unity, meaning consensus. And I chose to use 'achieve' since you that is often used with consensus, or in fact 'unity' or 'a harmonious state' So: "In this case reaching unity remained difficult." It works for me as a native English speaker, where nothing including the word 'unit' would.
But would a Portuguese speaker think that's the meaning? I think the point of this sentence is to show that atingir has more than one meaning: to hit a target or to attain or reach a goal. In this case unity is the goal we are trying to reach. Now it is becoming difficult
Well, I'm Brazilian, and that was my first thought indeed. (But I'm an engineer too, units are common in my head).
The unity meaning seems uncommon to me, but not wrong. It's somehow poetic. I can't see it used in life.
We'd probably use words like "união" (common) or "unicidade" (technical) to mean that. And "chegar a um acordo/consenso" to mean (to reach an agreement).
And I understand the primary meaning of "atingir" as "to hit (against something). We use that for targets and collisions in general.
It can be "to reach" too, but for that we have other common words as "alcançar" and "chegar a".
It's common to "atingir um objetivo" (to reach a goal), "atingir os 100km/h" (to reach 100 kilometers per hour). "Atingir um resultado" (to come to a result). But it's not common to use "atingir um acordo" (agreement) and "atingir a união". All of these are common to be seen with "alcançar" and "chegar a".
I'm not a native speaker, of course, so this is a very helpful distinction. It leaves me thinking that the sentence is not a very good example of how to use the verb. Could you use atingir if you are, say, a soldier trying to reach a military unit to rejoin it, or else trying to hit a military unit with a projectile?