The original manuscript is not extant here, but spacing between nearby extant fragments suggests that Oliver Cowdery initially wrote “canst thou not turn away from us”, which he then corrected by supralinearly inserting thine angar in 𝓞. Given his typical spelling of anger as angar in extant portions of 𝓞 (14 out of 17 times), Oliver probably spelled the word here in 𝓞 as angar.
Oliver Cowdery’s supposed initial omission in 𝓞 of thine anger was perhaps influenced by the phraseology “turn away from us”. Both the 1830 edition and the printer’s manuscript (each a firsthand copy of 𝓞 for this passage) agree by having thine anger. Moreover, there are nine other occurrences in the text of “turn away one’s anger” and seven of “one’s anger is (not) turned away”, including four in Helaman 11:11–17 and two nearby ones in this chapter of Helaman:
The reading of the current text is undoubtedly correct with its inclusion of thine anger here in Helaman 13:37.
Summary: The original text undoubtedly had the direct object thine anger in Helaman 13:37, the reading of both 𝓟 and the 1830 edition; it appears that in 𝓞, not extant here, this noun phrase was supralinearly inserted.