いい加減 has been used in the game Chrono Trigger but in every dictionary that I looked up for this vocabulary, I just found words as translation but in the game it's not translated as any of those words.
The English translations for "さ、いいかげん起きなさい" are:
"Come on, now! Out of bed with you!",
and in the retranslated version,
"Come on, get up already!"
Does iikagen mean "come on"? Why is it translated like that? Dictionaries don't put iikagen as "come on".
A translation is a translation. Its main purpose is to convey the general idea expressed in the original language for the speakers of the target language. Things get lost and things get added in the process.
「いい加減{かげん}」 all by itself does not mean "Come on!" at all if you want to know the truth. How could it? It is a na-adjective and not a verb of any kind to begin with.
Does that mean the translations you obtained from your sources are no good? No. They are actually valid translations. It makes good sense in the target language (English), doesn't it?
「いい加減」 used in the line 「さ、いいかげん起{お}きなさい。」 means that an action or state has reached a point where one wants to see it end soon. What is that action/state in the sentence in question? It is the sleeping by the person that is being asked to wake up.
Thus, the translator opted for what s/he opted for instead of a more "literal" TL like "You have slept long enough. Wake up, now!" Which one sounds better in English?
So many users here seem addicted to bilingual sources, but a question like this can be solved within seconds if one were willing to look up the word in a monolingual dictionary. Just read the definition 🈩-2 in デジタル大辞泉.
Note that for this particular meaning/usage, the 「いい」 part is pronounced 「いい{HH}」 and not 「いい{HL}」. The latter pitch accent is used when 「いい」 means "good".
The literal translation of いい加減 is "not too much, not too little, but just right" although when we actually want to mean that, we use よい加減 instead.
いい加減にしなさい or いい加減に〜なさい is used when someone, almost always a child, has been doing something very bad (in this case oversleep) for a while and the angry adult or parent wants to correct the behavior to make it "just right".
Considering that, "come on" may be just an idiomatic translation, but doesn't seem like a poor one to me. Actually, this dictionary lists "come on" as one of translations of いいかげんにしろ which is a stronger form of いいかげんにしなさい.
