Dont be deceived by his white hair and wrinkles Barristan Selmy is one of the most dangerous warriors to have ever lived in Westeros. Having been involved in hundreds of battles, Barristans experience in fighting all manner of opponents combined with the incredible talent at combat he has had since youth mean that he is still one of the most formidable warriors in the Seven Kingdoms. Indeed, it was arguably the greatest mistake made in the tyrannical reign of Joffrey Baratheon (or should it be Lannister?) when he dismissed Ser Barristain from the Kingsguard and subsequently gifted Daenerys Targaryen with one of her most valuable assets. In a fight with a Giant from the north, Selmys superior swordsmanship and footwork would allow him to avoid getting hit while hacking away at the Giants legs. His wealth of experience in battle would give him the tactical prowess to anticipate the Giants attacks to ensure that he went unscathed indeed, it would just take one hit from the brute to instantly kill the archetypal knight of Westeros. Whether he fought it in his youth or as an old man, Barristan Selmys sublime technical skill would enable him to defeat the massive beast.