Are "the Perfect" (at-Tāmm) and "the Severe" (ash-Shadeed) among the صحيح (authentic/valid) Names of Allah?

"Al-Tamm" (The Perfect/Complete) is not among the Beautiful Names of Allah, due to the weakness of the Ahadith in which it is mentioned. "Al-Shadid" (The Severe/Strong) is mentioned in the Quran as an attribution, and in a weak Hadith that enumerates the Names. Some scholars have counted it among the Names, but the preponderant opinion is that it is not. Severity (shiddah) is an attribute of Allah, meaning strength, or severity of punishment.