"sincerer" in the adjective sense
open and genuine not deceitful
"he was a good man, decent and sincere"
"felt sincere regret that they were leaving"
2. earnest, sincere, solemn
characterized by a firm and humorless belief in the validity of your opinions
"both sides were deeply in earnest, even passionate"
"an entirely sincere and cruel tyrant"
"a film with a solemn social message"
Source: WordNet® (An amazing lexical database of English)
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