Chaos

The Bane Sword has a 1/201 chance of killing Chaos instantly. If I spend the first 3 rounds using the Defense, let's say I survive 10 more rounds before he kills me.

1 - (200/201)^10 = 0.0487		Odds of Bane Sword working at some point when I fight Chaos.
(1 - 0.0487)^14 = 0.4975		Odds of Bane Sword NOT working at some point after 14 fights against Chaos.

If my math is right, that gives me about a 5% chance of killing him every time I make it to him. That means that I need to fight Chaos 14 times to have better odds than not of my Bane Sword working.

------------

With the Defense, my damage is 50, my hit% is 140, and its critical rate is 33/201.

Since Chaos has an evade stat of 100, I have a 156/201 chance of hitting him. That gives me a 123/201 chance of doing regular damage, and a 33/201 chance of doing a critical hit.

Chaos has an absorb rating of 100, so my regular hit will always do 1 damage when it connects. A critical hit will do between 51 and 101, averaging 76 damage. At my current hit%, I attack eight times a turn after casting FAST on myself.

[(123/201)1 + (33/201)76] x 8 = 104.7		Average damage I deal per turn.
2000 / 104.7 = 19.1							Amount of turns it will take to kill Chaos

We have to round this up to 20 turns, since there's no such thing as a tenth of a turn.

That means I need to have 20 consecutive turns in which Chaos doesn't cast CUR4, doesn't successfully cast SLO2, and doesn't do enough damage to make me waste a turn using CUR3. Every turn, Chaos has a 50% chance of casting a spell, and he can only cast up to 7 spells during those 20 turns (For now, I'll assume he never does enough damage to kill me, and his SLO2 misses for ease of calculations).

(20 choose 7)(0.5^7)(0.5^13) + (20 choose 6)(0.5^6)(0.5^14) + ... + (20 choose 0)(0.5^0)(0.5^20)

This is a binomial distribution, calculating the odds that Chaos only casts seven spells over 20 turns + the odds that he only casts six spells over 20 turns + the odds than he only casts five spells over 20 turns and so on, all the way up to not casting any spells over 20 turns.

This totals 0.1316 according to a calculator I found, which is actually a bit more than I expected. But we're not done yet!

At level 50, a Red Wizard has a magic defense of 118. SLO2 has an accuracy of 212, including the base accuracy of magic. That means that it has a (212 - 119)/201 = 46.27% chance of hitting me, and a 53.73%	 chance of failing.

If Chaos does end up casting SLO2 (meaning he casts exactly 7 spells over 20 turns), I will still lose 46.27% of the time.

(0.0518) + (0.5373)(0.5) = 0.3205			The odds of Chaos casting exactly 6 spells over 19 rounds + the odds of him casting SLO2 and it failing.

So if Chaos casts exactly 7 spells in 20 rounds, I have roughly a 32% chance of beating him.

(0.3205)(0.0739) + (0.0577) = 0.0813		Odds of killing Chaos through damage.
(1 - 0.0577)^12 = 0.4901					Odds of NOT killing Chaos through damage after 12 battles.

So I have about an 8% chance to kill Chaos through brute force, and a 5% chance to kill him with the Bane Sword. Of course, this doesn't take into calculation the odds that Chaos does enough damage to kill me within those 20 rounds, the odds that I go first on the 21st round, or the odds that I act second on the round he casts CUR4 (either of which would give me an extra round to kill him). Calculating all of that is beyond the scope of what I am willing to do for now.