Bismillah ir Rehman ir Rahim
The Compassionate,
The Merciful, The Clement, The Ever-Merciful
(Ar-Raheem, al-Rahim)
Qur'an 2:143
According to Dr Sharib:

'Al-Halim is the One Who does not lose self-control even when in anger,
excitement and wrath, and Who, in spite of possessing power, does not
hasten to take revenge.'

Forgiveness of, and forbearance towards, others are required to emulate
the name.

The effects of appropriate recitation safeguards against loss of power
and prestige. It can also be used effect improvement and progress in arts
and industry, or to save a boat from sinking.

see 'The 99 Most Beautiful Names of Allah' by Dr Zahurul Hassan Sharib

Some other references:

Al-Ghazali says that Al-Halim pertains to one who observes the
disobedience of the rebelious yet is not moved by anger or or wrath, nor
does he rush to take revenge though he is capable of it. He quotes Quran
16:61 - "If God should take men to task for their wrongdoing, He would
not leave on the earth one creature that crawls."

(Al-Ghazali - The Ninety-nine Beautiful Names of God. Trans. Burrel/Daher: ITS: 1992.)

It is a sign of one absorbed in inner worship and love of God that he is not
disturbed easily by the behaviour of others - as an adult is not moved
easily by the petty bickering of small children. Self control is of great
significance in spiritual development.

Bismillah ir Rehman ir Rahim
The Kindly, The Clement, The Non-precipitate,
The Mild, The Meek.
Qur'an 2:225
Allah will not
Call you to account
For thoughtlessness
In your oaths,
But for the intention
In your hearts;
And He is
Oft-Forgiving, Most Forbearing.
Laa yu-'aakhizu-kumul-laahu bil-laghwi fiii
'ay-maanikum wa
laakiny-yu-'aakhizukum-bimaa kasabat
quluubukum; wallaahu Ghafuurun Haliim.

(Qur'an 2:225 trans. Y. Ali).