Here is the story how Lord Ram eliminates Khara n Dushana n their army
The fourteen demons arrive at Ram's hermitage guided by Shuurpanakha and they wage a war with Rama. Ram then says Lakshmana. "Oh, Soumitra, stay here near Seeta as I wish to eliminate these demons who have trailed the path of that demoness to here." Lakshmana obeyed his brother's order.
Ram then warns those demons n asks them to return. But the fourteen demons, upraising their weapons unhesitatingly rushed towards Ram and they hurled lances towards him. Ram in turn shredded all of those fourteen lances only with as many arrows that are adorned in gold. Ram then in high wrath took up fourteen iron bolt like arrows that are whetted on whetstone and equaling the sun in their dazzle. Then he took up his bow, arched it, and aiming at the targeted demons released arrows. And by the force of their speed those arrows gored the chests of those demons, and then on coming out bedaubed with blood they swiftly penetrated into earth like snakes into snake pit. On seeing the demons falling onto ground that demoness Shuurpanakha got convulsed in rage, n she quickly fled from Panchavati to Trikantaka, the capital of Khara, n reported to Khara all about the destruction of those demons, in its entirety. She persuades him to wage a war against Rama and Lakshmana and annihilate them for they intruded into Dandaka and there is every possibility of onslaught by them on demons. Khara, the brother of Shuurpanakha starts out to wage war with Rama with fourteen thousand demons. Khara's army faces many bad omens. The army of demons readily inspirited for a battle quickly rushed towards those two princes, Rama and Lakshmana.
Ram perceives good omens of victory, but to safeguard Seeta he sends her away with Lakshmana to take shelter in a mountain's cave till the war is over. He said Lakshmana, "Preventive measures are to be effectuated for any imminent situation by any well-wishing person, or by a person with misgivings about a danger, or by a person of talent. Wield your bow, keep arrows ready at hand, and take Vaidehi with you and seek shelter in a impassable cave of a mountain overgrown with trees." Lakshman did as Ram wished
Ram stretched his awesome bow to examine the taut of bowstring, and even whipped arrows out of quiver and then adopted a mask of extreme wrath to eliminate all the demons. Here Valmiki has described Ram's wrath as wrath of Lord Shiva who after Sati's death decides to ruin Daksha's vedic rituals as
"The all-pacific aspect of that Ram then in his exasperation appeared to be like that of the all-ruinous Rudra, the wielder of bow called Pinaki, namely peaceful Shiva when enraged, at the time of Rudra's embarking on to ruin the Vedic ritual of Daksha Prajaapati."
Ram gives the demons enough time and warning, but as the atrocity is escalating, he uses one gandharva missile and many other arrows, which will devastate the entire army of Dushana's brute force. On seeing the killed demons all the surviving demons have become enervated and they are rendered incapable to make a move towards Ram. Rama eliminates fourteen thousand demons led by Duushana. Firstly, the forerunning demons are killed, next Duushana is routed, and then twelve other captains (Shyenagaami, Prithugviira, Yajnashatru, Vihamgama, Durjaya, Karaviiraaksha, Parusha, Kaalakaarmuka, Hemamaali, Mahaamaali, Sarpaasya, n Rudhiraaksha) who on knowing Duushana's downfall dashed towards Ram. Left behind are only two, Khara and Trishira, the chiefs of that demonic force in Janasthaana. Then on surveying that great demonic force which is eliminated by Rama in that staggering war, Khara then marched on to reach Rama in a huge chariot. Trishira, the demon, supersedes Khara to fight Rama at his turn. He hits Rama with arrows for which Rama says that it is no more than the patting with flowers. Then a combat follows and Rama eliminates Trishira in the battle.
Then Khara confronts Ram when all of his valiant warriors are eliminated. He wages a fearful war showing all his expertise in warfare. Khara even brings down the amour of Rama with his arrows. The combat of Rama and Khara takes a longer time as Khara is not easy-to-deal demon.
Khara shattered the bow of Rama with its arrow, at its fist-place, showing skill of his hand. Khara again on taking seven other arrows hit at the armour [crucial parts] of Rama, infuriately in that war and those arrows equal the radiance of Indra's thunderbolts. Then hitting with a thousand arrows at Rama of unequalled vitality, Khara blared a loud blare in that combat. Ram then takes Vishnu bow n rushed towards Khara. Then with arrows that are with golden fins and curved barbs Rama very angrily fragmented Khara's flag and flagstaff in that war. By that Khara is enraged and dashed four arrows onto Ram's body, also on chest, for Khara is aware of striking crucial parts/war tactics, as an elephant will be dashed with lancets. Ram with various arrows that are unloosened from the bow of Khara, is impacted and drenched are his limbs in blood, then Ram became indignant.
Ram then took Vishnu Bow n released six arrows targeting pointedly. Only one arrow on head, two on hands are set on and then with three demi-lune arrows Rama hit Khara's chest, verily. Then afterwards he with iron arrows that are sun-similar, infuriately shot at that demon, thirteen arrows in all, all are stone-grind. With one arrow the yoke of the chariot, with four, four of the dappled horses, and with eight the head of the charioteer of Khara are dismembered. With three arrows the three-pronged shaft from yoke to the base of chariot,] with two arrows the axel and with twelve arrows Khara's bow with its arrow are devastated.
Ram spoke these words forbiddingly albeit softly to Khara who lost his chariot in order to test whether Khara is ready to surrender or not, at least at this stage of loosing all equipment of war. Ram said, "Although you hold sway over a gigantic force abounding with elephants horses and chariots, you have perpetrated heinous deeds in Dandaka forests that are loathsome to all the worlds, that is unseemliest to this soldiery. One who causes suffering to living beings, besides being a transgressor and completely ruthless, he does not stand up for himself even if he were to be the lord of all the three worlds. All people will eliminate him, oh, nightwalker, who is imperious and an infringer of worldly routine, as they would eradicate a vicious serpent, in the event of its running across them. He who goes on performing evils selfishly, obsessively, heedlessly, more so delightedly, he will see the results of his own doings, like red-tailed-lizard on its eating self-destructive hailstones, obsessively and delightedly. The residents of Dandaka forest are the highly-propitious sages that tread the path of virtue, and oh, demon, what benefit you gain in killing them, really? Even if a fortune is made for a lavish living with an iota of merit, the evildoers, that too reprobates, further more those that are abominated by world will not last long, no more that petrified tree trunks. One who undertakes evildoings will definitely and seasonably reap their fruits, which in his case will be ghoulish, as with the flowering of trees according to season. In the world one acquires the fruit of profane acts not before long, oh, nightwalker, and it will be like venomous food devoured. I am the king who arrived to exterminate the lives of those that perpetrate hideous sins, and even of those that wish to do evils to the disapprobation of world…Now eliminated in war, you along with your army will tread behind those sages that were treading the path of virtue, on whom you have so far feasted in Dandaka forest…..Attack me as you wish... make an effort... you the knave of your clan..."
But Khara in reply said that he'll not surrender. Highly infuriated Khara hurled his mace towards Ram, around which there are superb golden cinctures, and which is extremely glaring like a thunderbolt. Forcefully discharged from Khara's hands that highly fiery and stupendous mace rendering trees and shrubs down to ashes darted towards Ram. Ram smashed it to smithereens with his arrows in sky itself. Ram and Khara exchange a haughty wordy duel. Khara then knitting his brows tightly saw everywhere for an assault weapon for use in that combat, and then he indeed found one not far away from him, namely a huge saala tree. He curled his lips in frown and started to extricate that Saala tree, and that great-mighty Khara on forcefully uprooting that tree with both of hands hurled it aiming at Ram, braying loudly and shouting at him 'you are dead...' utterly shredded Khara with a thousand arrows in that war. Khara then quickly bolted towards Ram. Then, Ram snatched an arrow which is similar to the Ritual-fire (given by Agastya) n released it towards Khara. That arrow hit the chest of Khara. Khara fell down on to earth n gets burnt by the radiation of that arrow. Gods and sages then showered flowery rain on Ram.
In the meanwhile Lakshmana exiting from the mountain cave came along with Seeta to their hermitage, and he is charmed at the victory of his brother Ram.
And Seeta on seeing her husband, the eliminator of enemies and accorder of happiness to sages, hugged her husband Ram, rejoicingly.