In the first version of problem 3646, e and bass found a nice additional solution. As bass mentioned, that solution is worth a problem of its own. Ok, here it is :)
The last white move, WB7, was a mistake - WC7 instead would have secured a jigo. How can Black win now?
(;GM[1]FF[4]CA[UTF-8]AP[CGoban:2]ST[2]
RU[Japanese]SZ[7]KM[0.00]
PW[Weiß]PB[Schwarz]AW[ba][cb][fb][gb][cc][dc][ec][gc][cd][ce][ee][fe][ef][gf][fg]AB[bb][ac][bc][fc][bd][dd][ed][fd][gd][be][de][af][cf][df][dg]C[No komi, no prisoners - Black to play and win!]
(;B[fa]CR[fa]
(;W[ea]CR[ea]
(;B[ca]CR[ca]
;W[da]CR[da]
;B[aa]CR[aa]
(;W[ab]CR[ab]
(;B[eb]CR[eb]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[With his next move, Black connects the ko and wins by one point. RIGHT])
(;B[ge]CR[ge]
;W[eg]CR[eg]
;B[aa]CR[aa]
(;W[eb]CR[eb]
;B[ca]CR[ca]
;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ba]CR[ba]C[White wins by one point!])
(;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ab]CR[ab]
;B[eb]CR[eb]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[This would be a one point win for black, but WB2 was a mistake!]))
(;B[eg]CR[eg]
;W[ge]CR[ge]
;B[aa]CR[aa]
(;W[eb]CR[eb]
;B[ca]CR[ca]
;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ba]CR[ba]C[White wins by one point!])
(;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ab]CR[ab]
;B[eb]CR[eb]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[This would be a one point win for Black, but WB2 was a mistake!])))
(;W[ca]CR[ca]
;B[eb]CR[eb]C[A double snapback, White is lost!]))
(;B[da]CR[da]
(;W[ga]CR[ga]C[White lives & wins])
(;W[eb]CR[eb]
;B[ca]CR[ca]C[White is dead, but WE6 was a bad mistake!])))
(;W[eb]CR[eb]
;B[da]CR[da]
(;W[ca]CR[ca]
;B[ea]CR[ea]C[This is a seki, so Black wins big!])
(;W[ea]CR[ea]
;B[ca]CR[ca]C[White is dead...])))
(;B[da]CR[da]
;W[ea]CR[ea]C[White lives & wins.])
(;B[ea]CR[ea]
;W[eb]CR[eb]
;B[da]CR[da]
;W[fa]CR[fa]C[White lives & wins.])
(;B[eb]CR[eb]
;W[ea]CR[ea]
;B[ca]CR[ca]
;W[da]CR[da]
;B[aa]CR[aa]
;W[ab]CR[ab]
(;B[fa]CR[fa]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[With his next move, Black connects the ko and wins by one point. RIGHT])
(;B[ge]CR[ge]
;W[eg]CR[eg]
;B[aa]CR[aa]
(;W[db]CR[db]
;B[ca]CR[ca]
;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ba]CR[ba]C[White wins by one point.])
(;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ab]CR[ab]
;B[fa]CR[fa]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[Black wins, but WB2 was a mistake!]))
(;B[eg]CR[eg]
;W[ge]CR[ge]
;B[aa]CR[aa]
(;W[db]CR[db]
;B[ca]CR[ca]
;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ba]CR[ba]C[White wins by one point.])
(;W[bf]CR[bf]
;B[bg]CR[bg]
;W[ab]CR[ab]
;B[fa]CR[fa]
;W[db]CR[db]
;B[aa]CR[aa]
;W[ga]CR[ga]
;B[ca]CR[ca]C[Black wins, but WB2 was a mistake.]))))