Is La ilaha illallah the best dhikr?

According to the hadith, "The best remembrance is 'La ilaha illallah'" [Jami at-Tirmidhi 3383]. Throughout the daily course of life, the only way to revive Iman is through La ilaha illallah, meaning "there is no god but Allah", as according to another hadith, "Revive your Iman through Lailaha" [Musnad Ahmad].

It is this dhikr of La ilaha which reaches the Throne of Allah, as Allah's Messenger ﷺ said, "When a person sincerely says 'la ilaha illallah', the doors of the sky are opened, until it reaches the Throne so long as he avoids major sins" [Jami at-Tirmidhi 3590].

There is the glad tiding of intercession by Allah's Messenger ﷺ for the person who says La ilaha, as he said, "The fortunate person who will gain my intercession will be that person who says 'La ilaha illallah' sincerely from his heart" [Sahih al-Bukhari 99].

The statement La ilaha illallah brings the servant to the highest levels of faith, as Allah's Messenger ﷺ said, "Faith has seventy-some odd doors, the lowest of which is removing something harmful from the road, and its highest is the statement 'La Ilaha Illallah.'" [Jami at-Tirmidhi 2614]

According to Mujaddid Alf Thani rahimahullah, "The seeker is to perform the Dhikr, la ilaha to the point that the heart is void of everything except for Allah" [Imam Rabbani, Maktoob 2, vol. 3].

In another letter he wrote, "One is to remain engaged in the Dhikr of Allah and except the 'Remembered one' (Allah) everything else should depart from his chest and there should not remain any sign and symptom of 'other than Allah' (masiwá) in him. Anything 'other than Allah' even as an illusion should not enter his heart. Even if one intentionally tries to visualize 'other than Allah' (ghair) in his heart, then this should not be availed due to that 'forgetfulness' which his heart has achieved about everything else, except the 'Remembered one'" [Imam Rabbani, Maktoob 84, vol. 3].