Not an easy one, for sure! Here's the best solution I could come up with:
* Setti 2 @ A
* We have (unusually) 5678 missing from a row, each. This will keep coming back.
* CE col 5: E5=3478, F5=178, B5=1238
* Setti 4/5 chain: B5!=8. Otherwise
-- 5 in col 4
-- J7=9 (via F7)
-- EF1=87 (single 8 in E)
-- BC1=34 (Setti 5)
-- Setti 4 conflict: 4 in all cols but not in J (J1=1, J7=9)
* UR J3!=23
* 2-fish 7 25
* Setti 58: if col 1 contains 5 it must miss 8 and vice-versa. No 58 in BC1
* UR A4!=5
* Settis 67
* HC / finned 2-fish (with a little good-will): F9!=2. Trivial if E8=1; if E8!=1, 2-fish 1 --> F6=1
* NT 134 @ FHJ3, no 9 in col 3
Solution/discussion of 'extreme' puzzle #654
Re: Solution/discussion of 'extreme' puzzle #654
Rübennase, you are right, the main key ist to use the setties combination right. Setti 4 and 5 help to decide h/l 5 and all setties especially 5, 8 and 1 help to decide h/l in A.
Re: Solution/discussion of 'extreme' puzzle #654
Thanks for checking, Cosmanita! Care to elaborate how you use Setti 1? I don't find much use for it, other than speed up the end-game. But I may be overlooking something nifty...