Psalm 145:6 "Men shall speak of the might of Your terrible (awesome) acts and I will declare Your greatness."

Verse 7 "They shall abundantly utter the memory of Your great goodness and sing of Your righteousness"

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These 2 verses talk about 2 things:

1. God's acts and character

2. What men is doing about God's acts and character

1. God's acts and character

God's acts

God is doing terrible or awesome acts ("terrible" is used to describe God's acts in the NKJV whilst "awesome" is used in the NJKV).

God's acts is "mighty" and "terrible" or "awesome". Why is it mighty? The word "might" is "ezuwz" meaning strength and fierceness in battle. God has won many battles for the children of Israel. The psalmist describes the victory in battles as mighty.

In fact, God's acts are so mighty that they verged on being "terrible". The acts are terrible because they are to be feared by the all.

To Israel's enemies, God's acts can be considered "terrible"but to those who obey, His acts can be considered "mighty"! So its 2 different ways of looking at the same thing (depending whose side we are on)!

God's character:

(i) Great (verse 6)
(ii) Good (verse 7) 
(iii) Righteous (verse 7) - "tsedaqah" refers to righteousness as God's attribute. It also refers to God ensuring that that we get justice in a case or a cause. Other meanings is to be ethically right or to be vindicated in a matter or thing.

2. What is men doing about the above?

(i) They are speaking of God's awesome acts and character
(ii) They are declaring of God's awesome acts and character
(iii) They are abundantly uttering the memory of God's awesome acts and character 
(iv) They are singing ("ranan" meaning to "sing, shout for joy, overcome, rejoicing") of God's awesome acts and character.