Ligurians weren't Celts, but a pre-Celtic people, and the Veneti of Cisalpine Gaul weren't that powerful. I mentioned Ligurians earlier. The powerful Veneti inhabited Armorica (modern Brittany). There were Boii there. None of the them though are really that strong and would probably be destroyed quickly by neighboring Gauls (under the Aedui), or by the Romans.