In the Ramayana, I've found several references of the Rakshasas fighting and defeating every species in the universe, with the exception of the Daityas.
6.65.13 - "Therefore, go like Yama the god of death, by taking a dart and a noose in your hand. Devour the Vanaras [monkeys] and the princes whose splendour is like that of the sun."
6.65.19;20 - Taking hold of that large spike tinted with the blood of enemies, shining like Indra's thunderbolt and equally heavy, capable of tormenting the Devas, Danavas, Gandharvas, Yakshas, and Nagas, wreathed in garlands of crimson flowers with excessive splendour and emitting flames by itself naturally, Kumbhakarna of great brilliance spoke to Ravana the following words:
And also, Ravana's conquests:
6.7.1;2 - Hearing the words of Ravana, those Rakshasas who were strong, stupid and without moral conduct, all raising up their joined palms and spoke to Ravana the king of Rakshasas, without knowing the strengths of their enemy's side (as follows):
"Oh, king! Our army, equipped with iron bars, javelins, double-edged swords, darts and sharp-edged spears, is very great. Why are you getting worried?"
"After proceeding to Bhogavati city (the abode of Nagas in Patala one of the seven regions under the earth), the serpents there were defeated by you. Kubera (the bestower of riches) who resides on the peak of Mount Kailasa, surrounded by many yakshas (a class of demi-gods) surrendered to you after doing a great battle."
"Oh, Lord! By your rage, Kubera who was boasting himself for his friendship with Lord Shiva (the Supreme Lord) and said to be a guardian of the world possessing great strength, was defeated by you in battle."
"Throwing down a group of Yakshas, after causing a flutter among them and taking them in prison, this aerial car (Pushpak) was procured by you from Mount Kailasa."
"Oh, the best of ogres! By Maya, the lord of Danavas, Mandodari his daughter was given to you in marriage, due to fear from you and duly desiring your friendship."
Oh, mighty armed! Madhu Kumbhinasa's (your sister's) husband, another ruler of Danavas, who was proud of his valour and who was difficult to be defeated, was taken into your subjugation, your having won a battle against him."
"Oh, mighty armed! After moving down to rasatala (the penultimate subterranean region), you conquered serpent-demons Vasukim Takshaka, Saukha and Jati were conquered by you and captivated as your subjects."
"Oh, annihilator of enemies, Commander of Rakshasas and the Lord! You after performing a battle for a year by you, mighty Danavas who were beyond destruction, who were valiant and who obtained boons (for immortality) were defeated using your own strength in combat. Several fascinating tricks also were learnt from them."
"Oh, illustrious king! Varuna's sons, valiant strong and who were followed by an army having four limbs (viz. elephants, chariots, cavalry and infantry) were defeated by you in a battle."
Oh, king! After entering a great ocean in the shape of Yama's realm, with a huge alligator in the form of death's rod of punishment, adorned with silk-cotton trees (bristling with thorns to be used a weapons), turbulent with a huge wave in the shape of noose of Kala (Time Spirit), with serpents in the form of Yama's servants and difficult to be conquered on account of mighty Jvara (Spirit presiding over fevers), and churning the sea in the form of Yama's forces, a great victory was obtained and death warded off by you. All the people there were delighted to see your good battle."
"The earth was filled, like with big trees, with many warriors [humans] who were strong with a courage equal to that Devendra (Lord of celestials).
"Oh, King! Rama was not equal to them in combat, by their valour excellence and energy. Those warriors, who were difficult to be overcome in battle, were overpowered and killed by you."
Oh, emperor! Why exertion to you? You remain here. Oh, emperor! This Indrajit alone can destroy the monkeys."
"Oh, emperor! After performing an excellent sacrifice to propitiate Mahesvara (the great lord shiva), a boon very rare to be obtained in the world, was acquired by him."
"Approaching that huge ocean of army of celestials, whose fish are lanes and spheres, whose guts thrown asunder as duck-weeds, whose turtles are the elephants, whose frogs are the teeming horses, infested with alligators in the form of (eleven) Rudras (gods of destruction) and (twelve) Adityas (sons of Aditi), with huge serpents in the form of (forty nine) Maruts (wind gods) and (eight) Vasus, having chariots horses and elephants for its volume of waters and the sandy elephants for its volume of waters and the sandy banks its infantry, Devendra (Lord of celestials) was captured by him [Ravana] and was impelled to come to Lanka (as a detenu)."
How come Daityas aren't mentioned? Was Ravana allied with the Daityas? Or had a neutral pact?