In English there is an idiom "I'll show you X," for example:
A: I think you're crazy.
B: Crazy? I'll show you crazy!
By this B means that he will give a demonstration of how crazy he is, probably in a manner A will not appreciate. I assume that I cannot translate it literally word for word, since using an adjective as a direct object is bad grammar in both languages. What is the most concise way to say this in German?
Basically
I will show you that which is crazy.
is used in German.
A: Ich denke, du bist verrückt!
B: Verrückt? Ich zeig dir gleich mal, was verrückt ist!
Notice the changes because it is spoken speech.
Ich zeige dir gleich das, was verrückt ist!
This is better understandable. "was" is refering to "das", the modal particle "mal"(or "einmal") is left out, and "zeige" is not contracted to "zeig".
Future is expressed through the adverb "gleich", meaning "in a moment". No auxiliary has been used.
I don't claim that this is the most common way or even popular to say, but it sounds right to me and some internet searches have shown some results of people using the construction.
