Pachy' don't deal large amounts of damage but their attacks will deal torpor. When fighting in the wild don't engage packs large then 3 if you only have basic weapons because they will knock you out quickly then have their way with you.
Tamed my pachy on craggs island, called it slappy. They are quite slow but the charge adds some speed in short bursts, I charge until out of stam and them set him to follow while he gets stam back and charge again, knocked out a couple of dodos while charging.
My tips are to use a bola if you have one to keep it in one place then knock out using stones on at tanqs. If you don't have a bola try finding one in an open area and pelt it with stones. To avoid its attacks run around in circles and reverse your movement when it is catching up or when it charges just walk out of its way and you can pelt it with stones while it charges as it is rather slow.
If your at a high level (101 or 99) taming a pachy can be very easy all you need is good accuracy with your bola and plenty of tranq darts... BUT never try to tame it when your a level 10 and below player it can become a nuisance