Now that you have finished the story, all that remains is to play through again on Hard. You probably won't have that much difficulty with any of the missions, perhaps with the exception of the final boss, and you don't have to worry about collecting any of the extra collectibles or narrative items. You can replay all chapters via timeline, which acts as a chapter select, instead of doing a brand new playthrough. However, I personally found it much easier to just start again and playthrough the whole game again, just on Hard. The only collectibles that I bothered with were the Chronon Sources to upgrade my powers.
Remember, to mop up the remaining achievements, you'll want to make the opposite choice to the first playthrough.
In Junction 1, you'll want to pick Hardline which will unlock;
In Junction 2, you'll want to pick Business which will pop;
In Junction 3, you'll want to pick (and trust) Hatch to collect;
And in Junction 4 you'll want to choose to Surrender and give into the Chronon Sickness, which will pop;
Finally, you'll want to deal with the final boss is a slightly more defensive way. Taking out the soldiers is your priority, and the most efficient way to do this would be to run around using time rush and using melee on the soldiers for a one-hit kill, before finding cover and repeating on all the others. Make the most of time dodge to avoid all incoming time blasts, especially the big ones.
After completing the game again on Hard, you'll unlock the final achievement;
Congratulations on your completion!
Find anything you think is wrong with this walkthrough? Help us fix it by posting in its Walkthrough Thread
This walkthrough is the property of TrueSteamAchievements.com. This walkthrough and any content included may not be reproduced without written permission. TrueSteamAchievements.com and its users have no affiliation with any of this game's creators or copyright holders and any trademarks used herein belong to their respective owners.