There are two hadeeth with wordings First hadeeth the heaviest on the scales of day of judgement is "la ila ha illa allaah" that is Tawheed and Second hadeeth is Heaviest on scales of day of judgement are good manners which is saheeh?? And if both are saheeh which encompases which hadeeth.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.

Umm Ad-Dardaa’ narrated from Abu Ad-Dardaa’ that the Prophet said: "There is absolutely nothing that is heavier on the scale than good manners.” [Ahmad and Abu Daawood - Al-Arna’oot and Al-Albaani classified this Hadeeth as Saheeh (sound)]

Moreover, Umm Ad-Dardaa’ narrated that Abu Ad-Dardaa’ said: “I heard the Prophet saying: "There is absolutely nothing that is put on the scale that will be heavier than good manners; and the person with good manners will attain the rank of the person of fasting and prayer.” [At-Tirmithi - Al-Albaani classified it as Saheeh]

As you see in the above two Ahaadeeth, the Prophet stated that there is nothing that is heavier on the scale than good manners.

As regards the first Hadeeth in your question, perhaps you are referring to the Hadeeth of ‘the card’ whose wording is as follows: ‘Abdullaah ibn 'Amr ibn Al-‘Aas narrated that the Prophet said: “Allaah will call a servant from my nation in front of all the creation on the Day of Judgment and He will open for him 99 registers and every register is as far as the human eye can see, and then will say: “Do you deny anything from this? Did my preserving angels [who record the deeds of people] wrong you? He [that man] will reply: “No, O Lord!” Allaah will ask him: “Do you have any excuse?” He will reply: “No, O Lord!” Allaah will say: “No, indeed you did one good deed with us and today you will not be wronged." So a card will be brought out in which is written: “I bear witness that La ilaaha illa Allaah (None has the right to be worshipped but Allaah) and that Muhammad is His Servant and Messenger." So, Allaah will say: “Bring out your scale.” The person will say: “O Lord, what can this card do compared to these 99 registers?” Allaah will say: “You will not be wronged today.” He [Prophet] said: “So, the 99 registers will be put on one side of the scale and the card will be put on the other side of the scale, so the 99 registers will be light in weight and the card will outweigh them, as nothing can outweigh the Name of Allaah.” [At-Tirmithi - Al-Albaani classified it as Saheeh]

This Hadeeth does not contradict the Hadeeth that we mentioned at the beginning of this Fatwa, because the meaning of the saying of the Prophet : “….as nothing can outweigh the Name of Allaah” - as stated by Al-Mubaarakfoori in Tuhfat Al-Ahwathi - is that nothing can outweigh or outbalance the Name of Allaah, meaning the sins cannot withstand the Name of Allaah; rather, the mention of Allaah outweighs all sins.”

You should know that good manners are a great fruit of the Fruits of Tawheed and so are all other good deeds. Allaah says (what means): {Have you not considered how Allaah presents an example, [making] a good word like a good tree, whose root is firmly fixed and its branches [high] in the sky? It produces its fruit all the time, by permission of its Lord. And Allaah presents examples for the people that perhaps they will be reminded.}[Quran 14: 24-25]

Allaah Knows best.