These brothers had a positive effect on Rome because they founded it. However, there was a negative side to it: Romulus murdered Remus and thus created the Roman empire.
Servius Tullius was the 6th king of Rome; however, he was overthrown by Tarquinius Superbus. While Servius Tullius positively changed many aspects of the Roman government, such as writing the Servian Constitution which granted plebeian independence, Superbus established an absolute despotism, and killed many before and during his rule in order to secure and maintain his position, deeming him a negative influence on Rome.
Superbus led Rome with absolute power, a negative ruling that opposes the republic Rome later had, which was the peak of the empire. He is known as Tarquin the Proud (arrogant), illegally overthrew and killed his brother Arruns Tarquinius, and he eventually was expelled. His style of ruling and arrogance was overall negative for Rome.
The Roman-Etruscan Wars was initiated by the Romans revolting against the Tarquinius Superbus, who was the Etruscan king of Rome. Thus, the monarchy in Rome had ended, which positively affected Rome by allowing for a republic to eventually form.
The Law of the Twelve Tables positively affected Rome by creating a written law set in stone. This prevented exploit and abuse by judges and protected citizens who did not know the laws that governed them.
A politician and intellectual that was very influential in the Roman Republic. Cato the Elder had a positive effect on the Romans because he was a perfectionist, honest, and strictly enforced Roman laws and made sure that public property was not abused. As a censor, Cato kept citizens in line and made sure that they behaved.
Hannibal’s invasion of Italy was initially very bad for Rome. Shocking the world, Hannibal successfully defeated the Romans causing many Roman allies and colonies in the areas conquered to defect to Hannibal’s side, causing Rome to lose much land. However, Rome pushed back and eventually defeated Hannibal decisively.
Julius Caesar led the transition of Rome into an empire, which was detrimental for Rome because the empire contained many ruthless emperors and dictators that abused the Roman citizens. This transition also involved many civil wars, which were bad for the Roman empire.
A Roman statesman who persistently opposed Julius Caesar and was known for his integrity. Cato the Younger had a positive effect on Rome as he abolished Catilinarian Conspiracy, allowing all involved parties to be sentenced to death without a trial, he was elected tribune of the plebeians, and opposed Julius Caesar.
Julius Caesar, Pompey the great, and Crassus teamed up and created the first triumvirate, taking apart the republic and establishing a consolidated empire. This negatively influenced Rome as the republic best represented the wishes of its citizens and the empire represented the interests of the emperor and he was free to do whatever he wanted, including neglect the people, which happened.
Pax Romana was overall a good thing for the Roman empire. For this period, the whole Mediterranean was a in peace and under a single government, allowing trade to flourish. However there are some negatives as poor people made meets end.
Trajan was a rarity: he was a decent or even good emperor. He expanded Roman borders and had new projects built nonstop. He was even called “Optimus” by his citizens. He allowed Rome to flourish.
Although Constantine was involved in the downfall of Rome itself, he led a successful transition into establishing a new capital, Constantinople. He introduced many Germans into the Roman military and played a significant role in introducing Christianity into the empire.
Valens was a very controversial leader in Rome and ultimately not a very good one. There were many revolts against Valens because many people hated him and his father-in-law. Also, after his brother Valentinian died, Valens took over the whole of Rome and showed no religious mercy and persecuted and even killed Catholics.
The conversion of Rome to Christianity was very detrimental for Rome because they lost all of their previous values and beliefs. This turned the majority of Christians into pacifists, preventing them from holding their own against barbarians that attacked the empire.
In 476, Romulus Augustus dies as the last western emperor. After his death, Rome itself began to crumble even more, with the Byzantine empire reconquering much land covered by Germanic kings, and eventually Rome was sacked by Visigoths. This is an overall negative event for Rome.