"deeply agree with" is correct and usable in written English.
You can use it when you want to express a stronger level of agreement than just "agree with." For example, you could say, "I deeply agree with his assessment of the situation."
Just as we yearn to tell stories, vent, and establish commonality, so we find ourselves wanting to captivate, charm -- particularly that one other person who deeply agrees with what we think and say, who buys our mythology and where we tell them we come from.
Deeply, I agree with Koonin that explaining the origin of replication cycles in general challenges any sort of thinking based on natural selection and goes beyond the classical evolutionary theory, in the sense that Darwinian evolution needs replication to happen and evolutionists need replication cycles (and descent) to reason.
And on most issues, she and I deeply agree.
Phrase used to agree with a deeply held conviction.
Ford said in a statement: "We deeply regret this incident and agree with our agency partners that it should have never happened.
"Many conservative commentators and leaders who I deeply respect, and who I agree with on practically every other issue, are disappointed about my involvement in this debate".
"How many of us are in the church and are deeply serious about our faith and agree with 100% of church doctrine?" Kaine asked the National Catholic Reporter in August.
Though I'm no longer a creationist, there are many people I still know and respect who agree with these beliefs deeply.
Even though I sympathize deeply with my parents, I don't agree with their choice for president – not even a little bit.
Anyone watching the currently rancorous, deeply partisan political debate would have to agree with her.
