General

@gekkegerrit: I don't know if Reboot bosses are stronger than regular worlds' bosses.

Google is your friend, someone made this thread one month ago on reddit
https://www.reddit.com/r/Maplestory/comments/5hknqw/required_range_for_reboot_bosses/

Seems accurate to the regular worlds too.

@hualicious: you are so right, i play Reboot and Bosses are much harder there. But because i play reboot, taht doesnt mean that everybody plays reboot , right ? lol.

200k for Normal HT, but it might take like 10 - 15 minutes.
300k should be enough for pink bean, might take like 15 minutes. Watch for DR.

Do you have a full set of CRA gear?

Normal Horntail - 50~60k (Mihile link skill is required and hopefully you got enough HP)
Easy Magnus - Not sure
Normal Root Abyss - 70-80k
Pink Bean - Not sure
Von Leon - Not sure

There is enough time to defeat most of the bosses if you are okay with killing a boss in 10 minutes or a bit longer. If your range is low, bosses like Pink Bean, Von Leon or Easy Magnus will take some time but you can kill them before the timer runs out.

And lol what gekkegerrit said about his estimated ranges, it is way too much

Normal Zakum - can be done with 10k range easily
Normal Hilla - 50k
Easy Horntail - not sure what minimum range, but it's really easy.

@sanjupm: aaaah, thx

@gekkegerrit: RNG is usually used as a short form for (Random Number Generator)

As far as i know
Normal Zakum 30k range
Normal Hilla 100k range
Easy Horntail 120k range

(is range and RNG the same ?_)