500s: Roman (Byzantine) wank
The Plague of Justinian hits Persia far harder than OTL while leaving the Romans relatively unscathed. After Justinian's death his successor stops with his conquests in Italy and North Africa and allow their gains to solidify rather than waste manpower going after the Franks and Visigoths.
The First Fitna is bloodier than OTL and never resolves itself, leaving the Middle East divided between the Umayyads and the Rashidun Caliphs, while Egypt goes independent under the command of Amr ibn al-As. Islam still spreads heavily into the Berber regions who eventually unite under a single leader, conquering most of North Africa and the constantly infighting Visigoths.
This happens in my signature timeline, where Charles Martel dies at Tours. In the chaos of the ensuing civil war the Frisians, alongside several other Frankish tributaries, break their ties with the Franks and go independent. Frisian raiders take to the channel, first raiding northern Gaul where the war has left the countryside without many defenders, then shifting their sights to Britain once the Franks regain enough strength to stop such raids. Eventually these raids turn into a campaign of conquest of southern Britain, with the loot from hundreds of cities, farms and monasteries being funneled back to Utrecht.
The vikings completely overrun the Anglo-Saxons, defeating Alfred and subjugating Wessex before collapsing. Rhodri the Great and his son, his only surviving male child, embark on a reconquest of Britain in the wake of the viking collapse, leaving behind a united Welsh kingdom spanning nearly all of Britain south of Northumbria.
The Magyars beat the Pechengs and remain on the Dnieper river. Bulgaria keeps Pannonia and is able to focus their full attention on the Byzantines. Simeon completes his conquest of Greece, reducing Byzantium's power in the region to a rump area around Constantinople. Simeon leaves a more capable heir to the throne when he dies and the empire endures until at least the end of the century.
Harald Hardrada is killed at the Battle of Nisa, which results in a Danish victory at the battle. Sven II subsequently retakes the throne of Norway. After consolidating Norway Sven launches an attack on England on the same grounds Hardrada used IOTL, but is successful in both defeating the Anglo-Saxons and pushing back the Normans.
No idea, I'm not familiar at all with this region during this time period.
England wins the Anglo-French war, retaining the Angevin's continental holdings and possibly even expanding them.
The Ottomans are killed in the cradle by Timur, allowing the Serbs to gobble up the remnants of the Latin and Byzantine empires.
The king of Portugal agrees to hire Columbus, meaning that the New World is initially claimed for him rather than for Spain. Colonialism proceeds much like OTL but with Spain and Portugal's empire's reversed.
Charles V manages to suppress the Dutch Revolt, keeping the low countries in the Spanish Empire.
Gustavus Adolphus survives Lutzen, and leads the Protestants to a complete victory. During the peace talks Sweden gains full control over the Baltic, and essentially turns the rest of Northern Germany into its puppets.
Same response as the Saxony one, sorry.
Muhamad Ali Pasha's descendants manage to keep the reactionary elements of Egypt in check. By the end of the century the Ottomans collapse due to butterflies, and the modernized Egyptian army stands ready to pick up the pieces.
Ataturk dies before he can stabilize Turkey, leading to a Greek victory in the Greco-Turkish war and the completion of the Megali Idea.