Below are 2 narrations that clearly say that there is no day the like of Shahadah of Imam Husain (as).

Hadith 1:

الهمداني، عن علي بن إبراهيم، عن اليقطيني، عن يونس، عن ابن أسباط، عن علي بن سالم، عن أبيه، عن ثابت بن أبي صفية قال: نظر علي ابن الحسين سيد العابدين صلى الله عليه إلى عبيدالله بن عباس بن علي بن أبي طالب (عليه السلام) فاستعبر ثم قال: ما من يوم أشد على رسول الله (صلى الله عليه وآله) من يوم احد، قتل فيه عمه حمزة بن عبد المطلب أسد الله وأسد رسوله، وبعده يوم موته، قتل فيه ابن عمه جعفر بن أبي طالب، ثم قال (عليه السلام): ولا يوم كيوم الحسين صلى الله عليه ازدلف إليه  ثلاثون ألف رجل يزعمون أنهم من هذه الامة، كل يتقرب إلى الله عزوجل بدمه، وهو بالله يذكرهم فلا يتعظون حتى قتلوه بغيا وظلما وعدوانا ثم قال (عليه السلام): رحم الله العباس فلقد آثرو أبلى وفدى أخاه بنفسه حتى قطعت يداه فأبدله الله عزوجل بهما جناحين، يطير بهما مع الملائكة في الجنة كما جعل لجعفر بن أبي طالب، وإن للعباس عند الله تبارك وتعالى منزلة يغبطه بها جميع الشهداء يوم القيامة

Narrated al-Hamadani, from Ali bin Ibraheem, from al-Yaqteenee, from Yunus, from ibn Asbaat, from Ali bin Salim, from his father, from Sabit bin Abi Safeyah who said:

Imam Ali bin Husain, the Master of the worshippers (as) looked at Ubaidullah bin Abbas bin Ali bin Abi Talib (as) then said, "There is not day more severe upon the Prophet of Allah (saww) then the day of Uhad in which his uncle Hamza (as), the lion of Allah (swt) and the lion of the Prophet (saww) was killed. And next to that day is the day of (battle of) Mu’ta in which his uncle Jafar bin Abi Talib (as) was killed."

Imam Ali bin Husain (as) then said, "And there is no day like the day of Husain (عليه السلام), thirty thousand men advanced towards Him who claimed to be from this (Islamic) community, all drawing closer to Allah (عز وجل) by (spilling) his blood. And by Allah, He reminded them but they did not take heed, until they killed Him unjustly with oppression and aggression."

Imam Ali bin Husain (as) then said, "May God have Mercy upon Al-Abbas, who preferred his brother to himself and sacrificed himself for his brother as a result of which both his hands were cut off (by the enemies). Allah (swt) substituted him two wings so that he can fly in Paradise along with the angels, like Allah (swt) did the same for Jafar ibn Abi Talib (as). Abbas (as) has such a high rank near the Blessed the Sublime Allah (swt) which all the martyrs will envy on the Resurrection Day."

[Source: al-Amali, Sheikh Sadooq, Pg. 277]

Hadith 2:

أن حسين بن علي بن أبي طالب (عليه السلام) دخل يوما على الحسن (عليه السلام) فلما نظر إليه بكى فقال ما يبكيك قال أبكي لما يصنع بك فقال الحسن (عليه السلام) إن الذي يؤتى إلي سم يدس إلي فأقتل به و لكن لا يوم كيومك يا أبا عبد الله

Mufazzal bin Imran Narrates from Imam Sadiq (as) from his Father (as) from his Grand Father (as):

Husain bin Ali bin Abi Talib (as) entered on the day of (Martydom) Al-Hassan (as) and wept when he looked at him. Imam Hasan (as) said: What makes you cry, he said Al-Hassan (peace be upon him) that which is brought to you (Posion)

Imam Hasan (as) said: "And there is no day like your day O'Aba Abdillah."

[Source: Al-Lahoof - Sayed ibn Taoos Pg.25]

Hadith 3:

Narrated that Imam Ali ibn Husain (عليه السلام) said,

ان الله وله الحمد إبتلانا بمصائب جليلة وثلمة في الاسلام عظيمة قتل أبو عبد الله الحسين عليه السلام وعترته وسبى نسائه وصبيته وداروا برأسه في البلدان من فوق عامل السنان وهذه الرزية التى لا مثلها رزية

Allah, for whom is all praise, tried Us with a severe calamity, and an irreparable loss in Islam.

Aba Abdillah al-Husain (عليه السلام) and His family were killed, and His women and children were taken captive. They displayed His head in the towns from the top of a spear. This is a calamity such that no other calamity is similar/equivalent to it.

[Source: al-Lahoof, Sayed ibn Taoos, Pg. 116]