Unstoppable Onslaught is a great way to initiate a teamfight as it deals damage and stuns multiple enemies, but you're restricted to a straight line so make sure you can land it.
You can also use Unstoppable Onslaught to ensure Sion escapes from unwinnable battles.
The best combo here is Roar of the Slayer to slow down an enemy, followed by Decimating Smash.
League of Legends Sion players will find him to be a complex champ to build out properly. You'll see that his build is modified when he is fighting either diversified or specialized team comps, demonstrating you shouldn't select the same Sion build every single game of League of Legends
The most essential items to include in your champ's build include: Heartsteel, Sterak's Gage, and Sunfire Aegis. Players who included these items in their setups had a much better winrate than those who went for other Sion builds. Similarly, if you are facing a varied enemy team arrangement, you should strongly consider getting him the Resolve, and Precision runes. In recent matches, he won the greatest percentage of his matches when using these runes.
We came up with our Sion build suggestions by analyzing 73,473 recently ranked League of Legends matches with him in them. We only recommend the highest winrate Sion builds that were built by ranked players enough times for us to advise them. With so many games in our dataset, we are very confident in our provided builds.