What are transfer credits in terms of Global Taxation

I've never heard of transfer credits per se, unless you're referring to transfer taxes when titles for assets are moved between various corporate forms or across borders. For transfer tax, aka estate tax, the taxable gain is the FMV - Adjusted Cost Basis. Depreciation recapture is taxed at ordinary rates and the cap gain is taxed at cap gain rates - short or long term depending on the holding period, but these rates are usually the same for corporations, but different for individuals.

There are also foreign tax credits - which are just tax credits up to 35 % of foreign source income (and credits for withholding taxes subject to country specific treaties with US), so if you pay taxes on only 25% of your foreign source income, then you are liable for the remaining 10% when that income is repatriated back to the states, but tax immediately if the income is subchapter F. FTC are for mainly CFCs - controlled foreign corporations whose stock (> 50%) is owned by a US tax paying entity.

There is also transfer pricing - i.e., income stripping by migrating IP, intercompany debt - across jurisdictions and setting up subcos to which the US parent pays heavy royalties to use various brands, trademarks, and sometimes inter-company debt with above arms' length interest rates to migrate income from high tax rate countries (US @40%) to lower tax rate countries like the Cayman Islands, Bermuda, Ireland , etc. which have zero or much lower tax rates.