It's highly unlikely that there really is no way to group the actions. It could be done by entity, by type of action, by work processes or by any other parameter. Maybe it's difficult to group them in a way that would allow drop-down lists, because the titles of the groups wouldn't be descriptive enough, but that's not the only option. You can turn the menu into a toolbar and group the items visually without the need to name the groups. Two-level toolbars aren't uncommon and that's a much better solution than a two-level standard menu. You can also try making a ribbon, but that does require a good taxonomy.
Also, there are solutions like fish-eye menus, designed specifically to save space on long menus. They are usually used with images, but text versions also exist.
Finally, if you're absolutely convinced that there's no way to group the items, then wrapping the names of the actions, so that each action becomes a two-row button, is still preferable to a two-row menu.