General

i have around 100% boss and a flat 200k range and i can solo leviathen with around 20-30 seconds to spare

I have 111k~123k clean, not counting the attack bonus from my Soul that can be gotten easily from Commerci. I can solo each of the bosses, although I cut close on time for the Red Leviathan, and good Dice rolls help out a ton. My Hyper skills are put into Octopunch, so it's much more effective, and I generally pop a Warrior Potion from New Leaf City for a +12 Attack boost(You could also use Guild Buffs). The other worthwhile stats to mention are 90% Boss, 31% Defense Ignore, 61% Critical Rate, 40% minimum critical and 60% maximum critical(I assume both those are the base).

Even if you can't kill the bosses for the Leviathan I believe you can just stand all the way to the left and he doesn't hit you, while you can tank through the Krakens(Green Kraken is easy though, stand on the right side to avoid the stuns they throw and touch damage). You lose out on bonus Denaros, but you can just work on unlocking every port before you worry about bosses.

@MrSaigon, I can confirm with 100% bossing and 200k+ range you can do it.

I have 110k range buffed on my bucc. Just under 100% boss dmg. I cannot kill blue Leviyatan dragon. I have only tried once, but iirc, I didn't come close to finishing. Maybe like half to 1/3 hp remaining

My current is 180k buffed 100% bossing post star force but haven't done commerci to tell you if It's enough.

100k lower range? Like border line 100k? Or like 150k -

You don't lose Denaros, the only way to fail is to die or disconnect. The time is counted against you for your bonus Denaros, however, so you may not get as many of those; you'll need a pretty high range to get a good time bonus.

The Leviathan bosses are sort of variable, since they have iframes on several of their moves for some reason, so if they spam them it can lower your damage per second. I think once you get to around 100k lower range clean you can solo all of them, but you'll be cutting it very close for the Red Leviathan. Once I can get on Maple I'll give you my range, I can solo all of them more or less, Red Leviathan is a bit of luck involved since I need a damage Dice(5 or 4, and both can impact your ability to beat the other bosses).

Haven't done enough runs to confirm that, but the 3 minutes may be off because I haven't done commerci for a while.
It should be v1.

For your bucc with 120k ranged buffed, which dragon is it? V1 or V2?

And is the time limit for each boss 3mins?

If you fail to kill a boss during the time limit you are given, it just dissapears for the round. You don't lose denaro, but you can lose profit for forfeiting the run.

For bosses All I know as a bucc with 120k range buffed, you can get lilyvithan (typing out of mind) to 2/3 hp in 3 minutes.