So I just tame an Allo solo. But it don't careful planning. You must first be willing to die a few times but at the end it's all worth it. They're always in groups so the first step is to lure them away from each other. The best way is to make one follow you and run towards a hill or cliff where they can stay. If you gain the high ground use a crossbow to damage one. It would eventually run away. Have at least 30 tranq arrows. It can surely take a beating but usually with 18-24 tranq arrows would KO it. The good thing is that since it's an allo, other allo's won't eat it or attack it
Try to make them fall into a ravine. Flyers help with this tactic. Or better, look for some that spawned or fell into one. There’s a ravine on my SP game where there are around 11 allos that fell into it. After getting them into a ravine, kill off all but the one you’d like to tame. Proceed in taming as usual.
Aggressive fast and run in packs! Definitely take out the ones you don’t want first, otherwise they will eat the your prize. Prime works fast but can be done with patients using the good ole chuck roast raw meat. I took the Alfa , down with 6-7 tranqs. To the back of her head while she ate her pack. Loyalty is not there strong suit. Careful they do those stupid circles when following you home(cliffs, trees rocks or other Dino’s ) which complicates your journey . Don’t let your Dino dangle. 😀