There is no single "best" strength drug out there becayuse not everyone responds the same to each steroid. For example, some people might say Tren gave them great results, but there are also plenty of people out there who barely gain any strength when using Tren.
In general, certain orals will provide the best (fastest) strength gains for the largest percentage of users. Most of the best strength building orals are DHT derivatives, with the exception of Halotestin. In addition, your best results will come from combining drugs which generate strength gains from different pathways, rather than combining drugs which work similarly.
With you using test as you base, if I was going to recommend a single 2-way combination for eliciting increases in strength as quickly as possible, it would be Superdrol & Halotestin. Or, Anadrol & Halotestin, although I give SD the upper-hand over Anadrol when both are dosed optimally. I would never combine SD & Anadrol, as they both tend to work similarly. Adding one to the other does not tend to produce significantly more strength gains, unless you weren't using enough of one or the other. However, Halotestin is another story and makes a great addition to either of those steroids.
As far as injectables go, Tren probably works the best for the largest number of people, but I doubt it would do much when added to a Test, SD, and Halotestin stack. Because both Halo and SD/Anadrol can be a bit harsh when combined at optimal dosages, I suggest a good liver supplement and that you keep your cycle short...no more than 6 weeks, max. This is not a stack would recommend in normal situations, except when prepping for the final 4-6 weeks before a powerlifting/strongman contest. Again, I recommend liver support with either of these cycles the entire way through. What follows below will provide incredible strength gains in all but the rarest of users and is for advanced users only. Beginners or intermediates will want to decrease the dose by about 50%. I want toi stress that this cycle needs to limited to occasional, short-term use only.
Weeks 1-5: SD @ 40 mg/day.
Weeks 1-5: Halotestin @ 40 mg/day.
or......
Weeks 1-5: Anadrol @ 100 mg/day.
Weeks 1-5: Halotestin @ 40 mg/day.
Of course, I don't recommend running these orals alone. You could if you wanted to and you would still make killer strength gains, but it is better (for a variety of reasons) if you add some test to it...and if you want to cover all your bases, toss some trenbolone in there as well. There is no need to use something like test suspension the day of the meet when running this stack, as the Halotestin alone supplies the androgenic potency of about 4,480 mg of testosterone per week. Halotestin has a MUCH stronger effect on the nervous sytem than testosterone, so why would make any sense to inject testosterne suspension on comp day when you are not only already using testosterone, but are also using a large dose of Halotestin...and maybe even trenbolone too? It wouldn't matter if you injected, 200, 300, or 400 mg of test suspension at once...it wouldn't do shit when you are already taking all that many potent androgens.
Of course, it is an absolute no-brainer that you should taking creatine as well. Creatine works through a completely different mechanoims than AAS to increase strength...and unless you are one of the few non-responders it will promote excellent increases in maximal strength. Most people who have not used creatine in a while will gain about 20 lbs on their big lifts within 4 weeks. That's pretty damn impressive considering it is a natural supplement. Creatine is mandatory. I recommend plain monohydrate--an ultra-micronized version.