4r1k1/p4pp1/2n2n1B/2b5/N6Q/P2q1N2/1r4PP/R4R1K b - - 1 23
Has the distinction of most possible moves in a rated game between humans, 79 to be exact.
positions(1) = 79
positions(2) = 3,319
positions(3) = 124,423
positions(4) = 2,859,642
positions(5) = 64,788,485
positions(6) = 1,029,681,307
go perft 7
a7a6: 25724485992
g7g6: 23360523846
a7a5: 24481458485
g7g5: 17671726160
g7h6: 14967259327
c6b4: 19844766321
c6d4: 18977857396
c6a5: 22363421438
c6e5: 20872320729
c6e7: 17798055165
c6b8: 19979471497
c6d8: 18612629844
f6e4: 20244239317
f6g4: 21079678036
f6d5: 29063835865
f6h5: 26438800449
f6d7: 27481210259
f6h7: 25604198905
c5g1: 24106298732
c5f2: 21329562819
c5a3: 24344154975
c5e3: 20089750437
c5b4: 22846539842
c5d4: 17865945604
c5b6: 22175123060
c5d6: 26913491992
c5e7: 18819535739
c5f8: 22059394770
b2b1: 18537064427
b2a2: 22054289160
b2c2: 21816641345
b2d2: 19775341144
b2e2: 22663202883
b2f2: 20105379478
b2g2: 22626039984
b2b3: 22576128310
b2b4: 24589795775
b2b5: 22019676813
b2b6: 21677667288
b2b7: 24132991495
b2b8: 22073605660
e8e1: 18728089318
e8e2: 21837960028
e8e3: 18818267119
e8e4: 20132952865
e8e5: 23753269631
e8e6: 22945531050
e8e7: 22180130672
e8a8: 20775044016
e8b8: 23474561273
e8c8: 21851127868
e8d8: 23309116861
e8f8: 19482358190
d3b1: 13516567004
d3d1: 16395719009
d3f1: 489045616
d3c2: 18249352216
d3d2: 18833926965
d3e2: 18358059878
d3a3: 17734097294
d3b3: 18954878557
d3c3: 20032367508
d3e3: 17463829328
d3f3: 14653152225
d3c4: 21253983339
d3d4: 17342646043
d3e4: 17907682413
d3b5: 16946491674
d3d5: 21203458584
d3f5: 22270466206
d3a6: 15769503995
d3d6: 19204368642
d3g6: 17064626235
d3d7: 20200728167
d3h7: 15056656391
d3d8: 17075280483
g8h7: 18534748945
g8f8: 20741141562
g8h8: 20456704030
Nodes searched: 1612761451963
Juts for kicks, I also ran the perft 7 after 22.Bxh6
1r2r1k1/p4pp1/2n2n1B/2b5/7Q/P1Nq1N2/1P4PP/R4R1K b - - 0 22
suspecting it would be greater, and it was ... 1.66 trillion
go perft 1 = 70
position fen 1r2r1k1/p4pp1/2n2n1B/2b5/7Q/P1Nq1N2/1P4PP/R4R1K b - - 0 22
go perft 7
a7a6: 29127646412
g7g6: 25843771858
a7a5: 28560153615
g7g5: 20371509427
g7h6: 17796839729
c6b4: 22225907484
c6d4: 21503922721
c6a5: 25780591909
c6e5: 23950019170
c6e7: 19692644021
c6d8: 21809655798
f6e4: 21662635884
f6g4: 23629078999
f6d5: 32074329747
f6h5: 29334285715
f6d7: 29424429212
f6h7: 28288422365
c5g1: 26357161858
c5f2: 25060458792
c5a3: 27893168032
c5e3: 22358283133
c5b4: 22969220146
c5d4: 18998499455
c5b6: 22232560712
c5d6: 28724736966
c5e7: 19614334476
c5f8: 23730310922
b8b2: 33071223186
b8b3: 27411136242
b8b4: 30018939563
b8b5: 28675187678
b8b6: 28662715916
b8b7: 31835417803
b8a8: 23982947209
b8c8: 23421126026
b8d8: 24377273659
e8e1: 25286504575
e8e2: 31981235535
e8e3: 24371667451
e8e4: 25757649632
e8e5: 31188466861
e8e6: 29881431761
e8e7: 28662299235
e8c8: 21953652108
e8d8: 24778812799
e8f8: 21729020371
d3b1: 16883743828
d3d1: 19595564803
d3f1: 526479889
d3c2: 24680495238
d3d2: 24470947574
d3e2: 23412260519
d3c3: 16481431995
d3e3: 19229550593
d3f3: 16896013177
d3c4: 23058719039
d3d4: 19590088065
d3e4: 20318552725
d3b5: 18524234188
d3d5: 24317674437
d3f5: 26034392075
d3a6: 18440072846
d3d6: 21380767814
d3g6: 19728271076
d3d7: 23132526647
d3h7: 17183693388
d3d8: 18504510830
g8h7: 22056171576
g8f8: 23285667613
g8h8: 23887983561
Nodes searched: 1657681099664