So if you want to avoid the alpha and you have a raft or flier in the south, aggro the alpha and either go away on the raft or fly away. Now when you come back, due to them being in the water, 2 will be on one side and one on the other, cancelling out the alpha effect. Use your flier (or get one) and go to a cliff and just shoot them. Note that this was on PS4 and it still takes three shots of a crossbow to knock it out with boosted torpor damage (300% to be exact) so good luck!

More Allosaurus Taming & KO Tips