"Try not to punch him."
When Greg Lestrade uses this as a word of advice to people who are about to meet Sherlock Holmes, he genuinely means it. Trying not to punch a man like that is not an easy task. He should know. He's done it three times.
He punched him on their first case
At this point in his life Greg had a full head of thick brown hair. He also had a supposedly loving wife and daughter. Then Sherlock came into the picture. Greg didn't think much of him at first. If anything he thought he was just another privileged and pompous prick who was born with a silver spoon in his mouth and didn't have to work at McDonald's to earn an education. He was brilliant, though. Too brilliant.
They met on a case and when they did Sherlock only had to look at Greg once to deduce everything about him from the death of his brother to the troubles in his marriage. He knew that he and Carol had been arguing that very morning, what they'd been arguing about and while Greg liked to consider himself a man with thick skin, bringing up the miscarriage was a step too far.
Sherlock went home with a broken nose.
He punched him after the Christmas party.
Greg was awestruck when Molly Hooper took off her coat. She had always been uniquely pretty, almost pixie-like in a way, but in diamonds and black velvet she was absolutely stunning. He'd always expected her to be bone-thin, but her pear shape not only took him by surprise, but was likely to give him questionable dreams that night.
Involuntary flirting ensued between the two of them until Sherlock, of course, interrupted with both a deduction of Carol's infidelity and Molly's present. Her appearance played a huge role in a rather embarrassing analysis and while Greg was proud of her for standing up to him there was something he needed to get off his chest to the consulting dickhead before he drove her home.
Sherlock spent the New Year recovering the bruise on his ribs.
He punched him when he was drunk.
When Greg's divorce with Carol was finalized he went straight from work to the pub. His goal was to get piss-drunk, find himself a girl and spend the night at her place. Naturally, Sherlock was the last person he wanted to run into. Apparently, he was conducting some kind of experiment that involved scotch and cyanide, but was willing to put it down a while to listen.
Greg was surprised at what a good listener Sherlock was. He wasn't sure if his understanding came from some knowledge of psychology or because he genuinely cared, but it helped to vent a little, especially to someone who wasn't likely to tell him he understood when he really didn't. After a few drinks, Greg became surprisingly aggressive when Sherlock called for a cab.
Sherlock didn't pay much attention to his split lip until he got home.
He hugged him when he came back.
Coming back from the dead, strangely enough, was not the most shocking thing that Greg had seen Sherlock do. He didn't even care how he did it or why. All he knew was that he was now fifty pounds poorer, thanks to a couple of colleagues. He had no idea what to think when he saw Sherlock alive and well, albeit a little beaten. He guessed it must have been a reunion with John.
Greg was feeling just about everything at once when Sherlock was only a few steps away from him: shock from his return from the dead, curiosity from how he did it, joy from seeing him again, anger from not seeing him for so long and other feelings he couldn't put a name to. In an overwhelmed fume, Greg seethed, dropped his lighter and cigarette and raised his arms.
Sherlock was expecting everything from the D.I. but a hug.