not realistic scene

You mean ZERO women, or just no women that you have met?

If the guy isn't handsome, chances are looks and facial expressions will not get him very far (no matter how hard he tries). Fassbender's character has sort of a "6th sense" on which girls will most likely be "slutty enough" to sleep with him on a first date.

Let me elaborate on this further...

Have you ever been out with a group of people and you (or your friends) have a sort of "gay-dar" that can pick out a homosexual male (or female for that matter)? If so, HOW do you think you were able to do it since no words or dialogue was exchanged? You pick up on things based on their NON-VERBAL cues, personality ticks, etc.

The scene in the subway with the married woman was actually a shocking (but realistic) scene. There's a lot of flirting on both sides going on - all with their eyes. Why is this married woman flirting? Perhaps she's unhappily married. Perhaps Fassbender reminds her of an old boyfriend, who knows? The point was to show her discomfort because she knew it was inappropriate to get turned on by the thought of having sex with Fassbender (a complete stranger). She reacted by quickly escaping to avoid temptation of crossing that line. It was interesting to note how she later returned to the subway dressed differently with hair done and make-up on (apparently to make herself appear more attractive while hoping & waiting for a 2nd chance to NOT "chicken out" with him). By that time Fassbender was over his demons. Or is he? There's a lot of very well done ambiguity throughout the film (also with the dysfunctional relationship with his sister).

Also, take note of the outing with his boss. The boss openly talks and verbally flirts with the girls at the bar. They are clearly not interested, and immediately singled out his boss as some kind of loser (he was trying too hard). Fassbender, on the other hand, had a look of mystery & confidence that was alluring. She didn't give the boss the time of day but instead hunted down Fassbender and was completely willing to boink with him - out in the open no less. The bottom line is some women gravitate to certain types of men than others. You are incorrectly assuming this means Fassbender's character can seductively look at just ANY person with eye contact and get them to sleep with him. No, that's not what I'm saying. Fassbender is able to search among a group and pick out the girls that are already attracted and aroused toward him (and that also have a personality that may be willing to sleep with him on a first date). This is how he functions. He isn't able to function in a normal healthy relationship, where intimacy take time and develops. The date scene was done exceptionally well to show the awkwardness that was felt on both sides (but mainly Fassbender's).

Poker players are well adept at picking up microscopic "tells" from another player at the table. A subtle shift in posture. A change in their breathing patterns, etc. I believe it may be possible for a sexual addict/predator to pick up on microscopic "tells" from another person that's trying to hide their arousal. Your posts on this forum suggest you may be young or not yet mature enough to have experienced or witnessed these types of things first-hand. Every person is a unique individual, and serves you no benefit to stereotype your false way of thinking how all women behave.