The sentence is almost 1:1 same in English:
I am one of the most wanted hackers in the world.
Ich bin einer der meistgesuchten Hacker der Welt.
Please notice, that this word is written together (thank you user_unknown) - keep reading for explanation.
Your confusion might result of the fact, that English superlatives are built using most (most beautiful, most powerful), whereas in German not (they are build with am ---sten, for example am schönsten).
Actually, meist is the superlative of viel (used as adverb in the meaning of frequent, see definition II here). Saying vielgesucht is perfectly correct and meaning searched a lot (or, in this context much wanted).
To complicate things a little more, we sometimes write things in German together, sometimes not. If written together, mostly a second meaning appears, often metaphorically. A nice example of this phenomenon is:
neuer Wagen (a newly bought car)
Neuwagen (a new, just produced car)
Same thing here:
meist gesucht would mean mostly wanted (but sometimes also not wanted)
meistgesucht means most wanted
Further reading Further reading 2