Ibn ʿAbd al-Wahhab only lived in the 18th century, so everything "extreme" before that point obviously cannot be attributed to his ideas. However, I'm going to limit my answer to the 20th century. If we're talking "extremism" in the modern era, the Islamic State of Iran was perhaps the important part of setting the mold. They're Twelver Shi'a, and obviously are not favored by the Salafis. Hezbollah is similarly Twelver Shi'a.

Even among Sunnis, there is tremendous variety. The Taliban is not Salafi--in fact, they're associated with Sufi orders, who in other circumstances the Salafis might not cooperate with. See Charles Kurzman's "Bin Laden and Other Thoroughly Modern Muslims" for more on the difference (it's a short article by a sociologist, but it's meant for a general audience--it was published shortly after 9/11). Pakistan's extremists are often called Wahhabis by their opponents, but the Deobandis and Ahl al Hadith are not quite Salafi. Though they are heavily influenced by Salafism and, arguably, parts of the movements are no longer distinguishable from Salafism, but they have their own intellectual heritage at least. Most importantly, there was a Muslim Brotherhood faction that was also quite influential and violent, the Qutbists--indeed, modern anti-state jihadism essential starts with with Said Qutb. See this post for more. This stream only really got mixed with Salafism by Osama bin Ladin in Afghanistan. Much of Muslim Brotherhood violence was in Egypt and against the Egyptian regime, but in the 70's and 80's, the violent faction started gaining ground elsewhere--interestingly, just as it was losing power in Egypt. Hamas, for example, is a Muslim Brotherhood off-shoot, and the 1979-1982 Uprising in Syra was also Muslim Brotherhood-led. The Muslim Brotherhood has moderated tremendously, however, and I can't think of a single Muslim Brotherhood-type movement that has advocated for violence since the 90's, other than Hamas (and other movement advocating violence against Israel).

As a side note, how and why and to what degrees Islamist movements have moderated is a big debate in political science these days. There isn't quite an agreement as to why, but the trend seems to be almost universally toward moderation (of existing organizations). However, the patterns of moderation don't follow those of Communist and Christian Democratic parties in Europe, who were moderated through participation in the system.