1) Pick up the Worldstones from Worldstone Caches using Silver Surfer for his Cosmic Worldstone achievement. This can also be done during Cosmic Weeks outside Big 10.

2) Use the daily Big 10 gift in cosmic terminals and pick the ES using Rocket Raccoon. His achievement requires picking up 50 ES in cosmic terminals and this should make it easier if you do it in 5 days.

3) Do Doop Sector Nine portals for easy "Doopicide" and "Cosmic Doopicide" achievements which give out 1 and 5 gifted Doop runes respectively. This can also be done during Cosmic Week outside Big 10.

4) If you are doing Burning Crusade achievements(2, 7, 9), these can easily be done in Bovine Sector portals(preferably level 55, takes 3 portals for the harder 7 and 9 achievements). This has also been said in the "Classic Firestar Achievement" thread in the forums.

4.1) Confidential Bovine Sectors and Bovineheim are the best places to do kill "x unspecified enemies" or "x elite unspecified enemies" using certain moves. ie. She-Hulk and Finishers only vs. elite unspecifieds.

5) Pick up the cosmic items dropped from Worldstone Caches(after Silver Surfer has grabbed the Worldstones) using Nova for his 500 cosmic items and 10 cosmic medallions achievement.

vadersdemise:

Thor also has an achievement where he needs to collect 100 odin marks, so you can open the rest of the reward boxes on hi (or all of them).

redlightning596 Actually the easiest way to do this achievement is to buy a level 70 legendary then refund it for Odin Marks. The 300 stack counts toward the achievement.

If you have any other tips and tricks for quick achievements, etc. doable right now, just leave 'em here for compilation.