After Hannibal crossed into Rome, he had to deal with the Roman general Tiberius Sempronius Longus who controlled a army of 45,000 men, roughly 10 to 15 thousand more men than his army.
Roman Casualties: 20,000 dead
Carthaginian Casualties: fairly light
With about 60,000 to 100,000 men and around 30 elephants, Hannibal made a expedition to Rome by going through the Alps. This task was thought to be impossible but Hannibal was able to get through the mountains within 14 days with 30% - 50% dead from hunger and cold.
Carthaginian Casualties: roughly 40,000 to 50,000
After Hannibal's victory at Trebia, Rome was a desperate to kill this Carthaginian General. Rome elected a new consul, Gaius Flaminius Nepos, to battle Hannibal on the field.
Roman Casualties: 15,000 to 20,000
Carthaginian Casualties: 1,000 to 3,000
Ignoring Fabius Maximus orders, the temporary dictator of Rome. Lucius Aemilius Paullus conjured up an army that number 85,000 to fight Hannibal's army of only 50,000. Hannibal used one of his most famous tactics to win his victory at Cannae. This is regarded as one of the most tactical triumphs of the ancient age.
Roman Casualties: 50,000 to 70,000 dead, 5,000 to 10,000 captured
Carthaginian Casualties: 8,000 dead or wounded
Since Hannibal was on Roman territory, Publius Cornelius Scipio invaded Iberia (modern-day Spain) in hopes of destroying Carthaginian Infrastructure.
Roman Casualties: 20,000 to 25,000
Carthaginian Casualties: unknown, estimated to be around 5,000
The Roman legions, now commanded by Scipio Africanus, made a second attempt to invade Iberia (known as Hispania) but this time with better results. Against Hannibal's younger brother Hasdrubal, Scipio's odds were with him since he had the numbers.
Carthaginian Casualties: 5,000 to 6,000 dead, 10,000 captured
Roman Casualties: 2,000